# Physics

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- Created by: jklos5899
- Created on: 14-11-19 12:23

Absolute Uncertainty

A measurement showing how large the uncertainty is, and has the same units as the quantity being measured

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Acceleration of free fall

The acceleration of a body falling under gravity

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Acceleration

The rate of change of velocity measured in metres per second squared.

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Accuracy

The degree to which a value obtained by an experiment is close to the true value

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Ammeter

A device used to measure electric current, connected in series with the components

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Ampere

S.I. unit for electric current

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Amplitude

The maximum displacement of a wave from its mean position, measured in metres

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Anomalous

Values in a set of data that do not fit the overall trend and so are judged not to be part of the inherent variation

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Antinode

The displacement of the particles in a stationary wave.

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Archimedes Principle

The upthrust exerted on an object immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the object displaces

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Area

A physical quantity representing the size of part of a surface, measured in metres squared

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Average Speed

A measure of the total distance travelled in a unit time

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Braking Distance

The distance a vehicle travels while decelerating to a stop

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Brittle

A material that breaks with little or no plastic deformation

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Centre of Gravity

The point at which the entire weight of an object can be considered to act

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Centre of Mass

The single point at which all of the mass of the object can be assumed to be situated. For a symmetrical body this will be in the centre.

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Closed System

Any system in which all of the energy transfers are accounted for, energy or matter cannot enter or leave

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Coherence

Two waves with a constant phase relationship

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Components of a Vector

The results from resolving a single vector into horizontal and vertical parts

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Components

Parts of electric circuits

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Compressive Force

Two or more forces that have the effect of reducing the volume of the object on which they are acting, or reducing the length of the spring

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Conductor

A material with a high number density of conduction electrons and therefore a low resistance

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Conservation of Charge

Physical law stating charge is conserved in all interactions, it cannot be created or destroyed

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Conservation of Energy

Physical law stating that energy cannot be created or destroyed, just transformed from one form to another or to another place. This is the situation in any closed system

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Conventional Current

A model used to describe the movement of charge in a circuit, from + to -

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Coulomb

Unit of electric charge, 1 C = 1 A x 1 s

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Couple

Two forces that are equal and opposite to each other but not in the same straight line

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de Broglie Equation

An equation expressing the wavelength of a particle as a ratio of Planck's constant and the particle's momentum, mv

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Deformation

The change in shape or size of an object. If it returns to its original shape then the deformation is elastic

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Degree Celsius

Unit for temperature

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Density

Defined as mass per unit volume

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Diffraction

When a wave spreads out after passing around an obstacle or through a gap

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Displacement

The distance travelled in a particular direction, measured in metres

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Displacement-Time Graph

A motion graph showing displacement against time for a given body

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Distance

How far one position is from another, measured in metres

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Drag Coefficient

A characteristic that determines the amount of drag that acts on an object

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Drag

The resistive force that acts on a body when it moves through a fluid

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Drift Velocity

The average velocity of an electron as it travels through a wire due to a p.d

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Ductile

Can be drawn into wires and show plastic deformation under tensile stress before breaking

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Efficiency

The ratio of useful output energy to total input energy

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Elastic Deformation

The object will return to its original shape when the deforming shape is removed

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Elastic Limit

The point at which elastic deformation becomes plastic deformation

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Elastic Potential Energy

The energy stored in a stretched or compressed object measured in Joules

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Elasticity

The property of a body to resume its original shape or size once the deforming force or stress has been removed

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Electric Charge

Current x Time. Measured in Coulombs

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Electric Current

A flow of charge. An S.I. quantity, measured in amperes and is a vector quantity

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Electrolyte

A fluid that contains ions that are free to move and hence conduct electricity

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Electromagnetic Wave

A self-propagating transverse wave that does not require a medium to travel through

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Electromotive Force

The energy gained per unit charge by charges passing through a supply, when a form of energy is transferred to electrical energy carried by the charges. Measured in Volts or Joules per Coulomb

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Electron Diffraction

The process of diffraction an electron through a gap

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Electron Flow

The movement of electrons from - to +

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Electron

Negatively charged sub-atomic particle. Conduction electrons travel around circuits creating an electric current

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Electronvolt

The kinetic energy gained by an electron when it is accelerated through a potential difference of 1 volt

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Energy

The stored ability to do work, measured in joules

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Equations of Motion

The equations used to describe displacement, acceleration, initial velocity, final velocity and time when a body undergoes a constant acceleration

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Equilibrium

When all the forces acting on an object in the same plane are balanced. There is zero net resultant force and in terms of motion, the object is either stationary or at constant velocity

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Error Bars

Represent the absolute uncertainty in measurements and can be plotted in x and y directions

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Extension

The change in length of an object when subjected to a tension, measured in metres

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Fiducial Mark

An object placed in the field of view for the observer to use as a point of reference

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First Harmonic

In the fundamental mode of vibration, the length of the string is half the wavelength. This produces the lowest possible frequency called the first harmonic

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Fluid

A material that can flow from one place to another

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Force Constant

The constant of proportionality in Hooke's Law measured in newtons per metre

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Force

A push or pull on an object measured in newtons

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Free Fall

When an object is accelerating under gravity

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Frequency

The number of oscillations per unit time, measured in Hertz

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Fundamental Frequency

The lowest frequency in a harmonic series where a stationary wave forms

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Fundamental Mode of Vibration

Where the length of a string is half the wavelength, producing the lowest possible frequency called the first harmonic

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Fuse

An electrical component designed to heat up, melt and break the circuit when a specified amount of current passes through it. Used as a safety device

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Gamma Rays

A form of electromagnetic wave used for cancer treatment

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Gradient of a Graph

The change in y-axis over the change in x-axis

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Gravitational Force

The force due to a gravitational field acting on an object's mass

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Gravitational Potential Energy

The energy stored in an object by virtue of the object being in a gravitational field, measured in Joules

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Hard

Materials that resist plastic deformation by surface indentation or scratching

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Harmonics

Whole number multiples of the fundamental frequency of a stationary wave

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Hooke's Law

The extension of an object is proportional to the force that causes it, provided that the elastic limit is not exceeded

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Impulse

The product of a force and the time taken for which the force acts

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Infrared

A form of electromagnetic wave used in remote controls

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Instantaneous Speed

The speed of an object at a given moment in time

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Insulator

A material with a small number density of conduction electrons and therefore a very high resistance

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Intensity

The rate at which energy is transferred from one location to another as the wave travels through space, perpendicular to the direction of wave travel.

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Interference

The addition of two or more waves that results in a new wave pattern

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Internal Resistance

The resistance to electric current of the materials inside chemicals, wires or components. When current flows, energy is transferred to these materials, resulting in the terminal p.d dropping

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I-V Characteristic

A graph to show how electric current through a component varies with a potential difference across it

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Joule

A unit of energy. 1 J is the work done when a force of 1 N moves its point of application 1 m in the direction of the force

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Kelvin

S.I. unit of temperature

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Kilowatt

Unit of power. 1 kW = 1000 W

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Kilowatt-Hour

1000 watts for 3600 seconds

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Kinetic Energy

The work an object can do by virtue of its speed, measured in Joules

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Kirchhoff's First Law

The sum of the currents entering any junction is always equal to the sum of the currents leaving the junction

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Kirchhoff's Second Law

The sum of the e.m.f is equal to the sum of the p.d. in a closed loop

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Light Dependent Resistor

A component that changes its resistance with changes in the light intensity. Dark = High, Light = Low

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Light Emitting Diode

A component that only allows electric current to pass through it in one direction and that emits light when a p.d. is applied across it

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Longitudinal Wave

A wave where the oscillations are parallel to the direction of wave propagation

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Lost Volts

The difference between the e.m.f. and the terminal p.d. when charge flows in the cell

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Malleable

Can be hammered or beaten into flat sheets and show extensive plastic deformation when subjected to compressive forces

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Malus' Law

A physical law describing the change in intensity of a transverse wave passing through a Polaroid analyser

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Mass

S.I. quantity, measured in kilograms

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Microwaves

A form of electromagnetic wave used in mobile phones

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Moment of a Force

The product of a force and the perpendicular distance of its line of action from the point of axis. Also called turning moment

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Monochromatic Light

Light waves with a single frequency or wavelength

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Newton

The force that causes a mass of 1 kg to have an acceleration of metre per second every second

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Nodes

Points in a stationary wave at which there is no displacement of the particles at any time

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Ohm

Unit of resistance

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Ohm's Law

The current through a conductor is directly proportional to the potential difference across it, provided that physical conditions remain constant

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Order

The number of the pattern on either side of the central maximum

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Parallel Circuit

A type of the circuit where the components are connected in two or more branches and therefore provide more than one path for the electric current

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Percentage Difference

The difference between two values, divided by the average and shown as a percentage

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Percentage Uncertainty

The difference between a measured and a true value expressed as a percentage

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Period

The time taken for one complete pattern of oscillation, measured in seconds

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Phase Difference

The difference by which one wave leads or follows another. In-phase waves are in step with each other. A completely out-of-phase wave is half a wavelength in front og the other.

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Photocell

A component that reduces its resistance when light shines on it due to photoelectric emission of electrons

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Photoelectric Effect

The emission of electrons from the surface of the material when electromagnetic radiation is incident on the surface

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Photon

A quantum associated with electromagnetic radiation

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Plane-Polarised Wave

A transverse wave only oscillating in one plane

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Plastic Deformation

The object will not return to its original shape when the deforming force is removed, it becomes permanently distorted

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Polarisation

The process of turning an unpolarised wave into a plane-polarised wave

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Polymeric

Made of long chains of molecules called polymers

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Polymeric Material

A material made of many smaller molecules bonded together, often making tangled long chains. These materials often exhibit very large strains

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Potential Difference

The energy transferred per unit charge

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Potential Divider

A type of circuit that uses two resistors in series to split or divide the potential difference of the supply in a chosen ratio so that a chosen p.d. can be provided to another device or circuit

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Potential Energy

A form of stored energy

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Power

The rate of doing work, measured in watts

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Precision

The degree to which repeated values, collected under the same conditions in an experiment, show the same results

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Pressure

Force per unit area at right angles to the area

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Principle of Conservation of Energy

The total energy of a closed system remains constant. Energy can neither be created or destroyed, only transferred from one form to another

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Principle of Conservation of Momentum

The total momentum before a collision is always equal to the total momentum after the collision, provided that no external forces are involved

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Principle of Moments

For an object to be in rotational equilibrium, the sum of the clockwise moments must equal the sum of the anticlockwise moments

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Progressive Waves

Waves that transfer energy away from a source

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Quanta

The plural of quantum

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Quantum

A small discrete unit of energy

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Radian

Unit of angle or phase difference. One radian is the angle subtended at the centre of a circle by an arc of circumference that is equal in length to the radius of the circle

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Radio Waves

A form of electromagnetic wave used in telecommunications

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Random Errors

Give measurements that are scattered randomly above and below the true value when the measurement is repeated. A better result can be obtained by finding by finding the mean value of the results of several readings

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Reflection

When waves rebound from a barrier, changing direction but remaining in the same medium

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Refraction

When waves change direction when they travel from one medium to another due to a difference in wave speed from one medium to another

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Resistance

A property of a component that regulates the electric current through it. Measured in ohms

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Resistivity

The ratio of the product of resistance and cross-sectional area of a component and its length

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Resolution of Vectors

Splitting a vector into vertical and horizontal components

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Resultant Force

A single force that has the same effect as the sum of all the forces acting on a body

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Resultant Vector

The sum of the two vectors forms the third side of the triangle

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Scalar

A quantity that has magnitude but no direction

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Semiconductor

A material with a lower number of conduction electrons than a conductor and therefore a higher resistance

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Series Circuit

A type of circuit where the components are connected end to end and therefore provide only one path for the electric current

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Significant Figures

The number of digits in a measured or calculated quantity that have a meaning and about which we can be certain

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Spectrum

A collection of waves with a range of frequencies

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Speed

The distance travelled per unit time

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Spring Constant

Force per unit extension

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Standing Wave

An alternative name for a stationary wave

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Stationary Wave

A wave forned by the interference of two waves travelling in opposite directions

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Stiffness

The ability for a material to resist a tensile force

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Stopping Distance

The sum of the thinking distance and braking distance

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Strain

Extension per unit length. Has no units and is dimensionless

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Stress

Force per unit cross-sectional area. Unit of Pa

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Superposition

The principle that when two or more waves of the same type exist at the same place, the resultant wave will be found by adding the displacements of the individual waves

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Systematic Error

An error that does not happen by chance but instead is introduced by an inaccuracy in the apparatus or its use by the person conducting the experiment

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Tensile Force

Usually two equal and opposite forces acting on a wire in order to stretch it. When both forces have the value T, the tensile force is also T, not 2T

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Tensile Stress

The tensile force per unit cross-sectional area

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Terminal p.d.

The potential difference recorded across the terminals of a cell. The difference between the e.m.f. and the terminal p.d. when charge flows is called lost volts

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Terminal Velocity

The velocity at which the objects drag equals its accelerating force. Therefore there is no resultant force and zero acceleration

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Thermistor

A component that changes its resistance based on its temperature. An NTC thermistors resistance reduces as the temperature increases

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Thinking Distance

The distance travelled from seeing the need to stop to applying the brakes

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Threshold Frequency

The lowest frequency of radiation that will result in the emission of electrons from a particular metal surface. For most metals, this occurs in the ultraviolet region

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Thrust

A type of force due to an engine

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Time Interval

S.I. quantity, measured in seconds

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Torque

The turning moment due to a couple is the product of one of the forces and the perpendicular distance between them. The units are N m

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Transverse Wave

A wave where the oscillations are perpendicular to the direction of the wave propagation

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Triangle of Forces

If three forces acting at a point can be represented by the sides of a triangle, they are in equilibrium

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Turning Forces

Forces that if unbalanced, will cause a rotation

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Ultimate Tensile Strength

The maximum stress a material can withstand while pulled or stretched before it fails or breaks

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Ultimate Tensile Stress

The maximum stress that can be applied to a material before it breaks

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Ultraviolet

A form of electromagnetic wave that causes sun tanning

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Upthrust

A force on an object due to a difference in pressure when immersed in a fluid

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Vector

A quantity that has magnitude and direction

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Vector Triangle

A type of scale diagram with two vectors, drawn tiptotail, to show how they can be added together

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Velocity

The displacement per unit time, measured in metres per second

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Velocity-Time Graph

A motion graph showing velocity against time for a given body

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Volt

Unit of potential difference and e.m.f.

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Voltmeter

A device used to measure the p.d. across a component. Is connected in parallel across a component

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Volume

A physical quantity representing how much 3D space an object occupies, measured in metres cubed

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Watt

Unit of Power

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Wave

A series of vibrations that transfer energy from one place to another

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Wavelength

The smallest distance between one point on a wave and the identical point on the next wave. Measured in metres

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Wave-Particle Duality

The theory that all objects can exhibit both wave and particle properties

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Weight

The gravitational force on a body, measured in newtons

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Work Done

The product of the force and the distance moved by the force and the force in the direction of movement

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Work Function

The minimum energy required to release an electron from a metals surface, overcoming the electrostatic attraction between the electron and the positive metal ions

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Worst Fit

The worst acceptable line, still passing through all of the error bars. This will be either the steepest possible line of fit, or the least steep line of fit

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X-Rays

A form of electromagnetic wave used in X-Ray photography

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Young Modulus

The ratio between stress and strain, measured in pascals

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Youngs Double Slit Experiment

An experiment demonstrating the wave nature of light via superposition and interference

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Zero Error

A type of systematic error caused when an instrument is not properly calibrated or adjusted, and so gives a non-zero value when the true value is zero

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Absolute Scale of Temperature

A temperature scale which is independent of the properties of any specific substance. Measured in Kelvin

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Absolute Zero

The temperature at which a substance has minimal internal energy. The lowest limit of temperature

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Absorption Line Spectrum

The pattern of dark line in a continuous spectrum from a light source, caused by light passing through an absorbing medium such as gas. The dark lines represent the wavelengths that are absorbed

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Acoustic Impedance

Defined by the equation Z = pc. Where p is the density and c is the speed of sound in a material

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Activity

The number of nuclear decays per unit time. An activity of one decay per second is called one becquerel

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Alpha-Particle

A particle comprising two protons and two neutrons ejected from the nucleus during radioactive decay. It is identical to a helium nucleus and is emitted due to its unusually high stability as a particle

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Alternating Current

Electrical current that reverses its direction with a constant frequency.

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Angular Velocity

The rate of angular rotation, measured in radians per second

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Annihilation

The process by which a particle and an antiparticle interact and their combined mass is converted into energy.

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Antiparticle

A particle of antimatter that has the same rest mass but, if charged, an equal and opposite charge to its corresponding particle.

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Astronomical Unit

The mean distance from the centre of the Earth to the centre of the Sun

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Attenuation

A gradual decrease in intensity

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Attenuation Coefficient

A constant used to calculate how the intensity of X-Rays decreases as they pass through a material.

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Avogadro Constant (Na)

The number of particles in one mole of a substance

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Beta-Minus Decay

Decay in which a neutron in the nucleus breaks down into a proton under the influence of a weak nuclear force, and a beta-minus particle and an electron antineutrino are emitted. A beta-minus particle is an electron.

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Beta-Particle

A high-speed electron emitted from the nucleus during beta decay. It is produced when a neutron changes into a proton.

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Beta-Plus Decay

Decay in which a proton in the nucleus breaks down into a neutron under the influence of the weak nuclear force, and a beta-plus particle and an electron neutrino are emitted. A beta-plus particle is a positron

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Big Bang Theory

States that the universe was created from a single point where all of the universe's current mass was situated. At the time of its creation, the universe was much smaller, hotter, and denser than it is now. Time and Space were created at the Big Bang

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Binding Energy

The minimum energy required to separate a nucleus into its constituent parts

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Black Hole

The core of a massive star that has collapsed almost to a point. The density is so great a strong gravitational field is created. Appears black due to the escape velocity being greater than the speed of light

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Boltzmann Constant

A constant used when relating the temperature of a gas to the mean translational kinetic energy of the particles in the gas. It can also be thought of the particles in the gas.

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Boyle's Law

States that the volume of a fixed mass of gas is inversely proportional to the pressure exerted on the gas, under conditions of constant temperature.

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Brownian Motion

The random movement of small visible particles suspended in a fluid due to collisions with much smaller, randomly moving atoms or molecules of the fluid.

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Capacitance

The quantity of charge which can be stored per unit potential difference. Unit is Farad

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Capacitor

A circuit component that stores energy by separating charges onto two electrical conductors with an insulator between them. One plate becomes positively charged and one becomes negatively charged

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Carbon Dating

A technique used to determine the age of organic matter from the relative proportions of carbon-12 and carbon-14 isotopes that it contains, using the half life of carbon-14

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Centripetal Acceleration

The acceleration of an object moving with uniform circular motion. The centripetal acceleration is directed radially inwards towards the center of the circle.

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Centripetal Force

The resultant force on an object, acting towards the centre of the circle and causing the object to move in a circular path.

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Chain Reaction

the sequence of nuclear reactions produced when an induced nuclear fission reaction triggers more than one further fission reaction

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Chandrasekhar Limit

The maximum possible mass for a stable white dwarf star, equal to 1.4 times the mass of our Sun. Stars above this limit will collapse further to become black holes or neutron stars.

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Collimator

A device for producing a parallel sided beam of electromagnetic radiation

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Compton Scattering

The effect whereby an X-Ray deflected by an interaction with an orbital electron has a longer wavelength than its original wavelength. The electron is ejected from the atom at high speed.

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Computerised Axial Tomography (CAT)

A process using multiple X-Ray scans to produce images of 'slices' through the body in one plane, in order to produce a 3D image.

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Continuous Spectrum

A spectrum that appears to contain all wavelengths over a comparatively wide range.

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Control Rod

A rod that can be lowered into the core of a nuclear reactor, absorb neutrons and slow down the chain reaction. Usually made of Boron

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Cosmic Microwave Background Radiation (CMBR)

Microwave received from all over the sky originating from after the Big Bang, when the universe had cooled to 3000 K.

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Cosmological Principle

States that on a large scale the universe is Isotropic (the same in all directions) and homogeneous (of uniform density).

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Coulomb's Law

States that the electrical force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of their seperation.

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Damping

Damping forces reduce the amplitude of an oscillation with time, by removing energy from the oscillating system

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Dark Energy

A type of energy that permeates the whole universe and opposes the attractive force of gravitation between galaxies via the exertion of negative pressure. It is not detected directly however it is known to exist due to the universe accelerating

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Dark Matter

Matter which cannot be seen and does not emit or absorb EM radiation. It is not directly detected, however detected indirectly due to its gravitational effects relating to either the rotation of galaxies or by gravitational lensing of starlight

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Decay Constant

The probability that an individual nucleus will decay per unit time.

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Doppler Effect

The change in wavelength caused by relative motion between the wave source and the observer.

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Driving Frequency

The frequency of the driving force applied to an oscillating object

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Electric Field

The region around a body in which other charged bodies will feel a force due to the electric charge of the body

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Electric Field Lines

Show the shape of the field. The direction of a field line at a point is the direction a positively charged would take if placed in that point.

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Electric Field Strength

The force per unit positive charge. The force that a charge of +1C would experience if placed at that point in a field. Units are Newtons per Coulomb

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Electric Potential

The work done per unit positive charge to move that charge from infinity to a point in an electric field.

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Electromagnetic Induction

The process of inducing an e.m.f. in a conductor where there is a change in magnetic flux linkage across the conductor.

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Electron Degeneracy Pressure

The pressure that stops the gravitational collapse of a low-mass star. This is the pressure that stops a neutron star from collapsing in on itself.

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Emission Line Spectrum

The spectrum of frequencies of electromagnetic radiation emitted due to electron transitions from a higher energy level to a lower one within an atom.

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Energy Levels

Electrons can only exist at certain energy values within an atom, occupying specific orbits at discrete energy levels

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Equation of State of an Ideal Gas

pV=nRT

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Escape Velocity

The minimum launch velocity required to move an object from a point in a gravitational field to a point at infinity

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Exponential Decay

Where the quantity decreases at a rate that is proportional to the magnitude of the quantity at that time.

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Faraday's Law

Faraday's Law of electromagnetic induction states that the magnitude of the induced e.m.f. is equal to the rate of change of flux linkage

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Farad

The unit of capacitance. One farad is equivalent to one coulomb per volt

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Fleming's Left Hand Rule

Shows the direction of the force on a conductor carrying a current in a magnetic field. Force = Thumb, Field = First Finger, Current = Second Finger. All at right angles to each other.

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Forced Oscillations

Oscillations where an external force or driving force is applied to keep the body oscillating. The system oscillates at the frequency of the driving force that is causing the oscillations

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Free Oscillations

Oscillations where there is no external force or driving force. The system oscillates at its natural driving frequency

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Fundamental Particles

Particles that cannot be broken down into smaller components

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Gamma Camera

Detects gamma photons emitted from a patient given a radioactive tracer. This is used to produce a real time image of the path of the tracer through the body

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Gas Pressure

Acts in all directions at a point inside a gas, such as inside a star.

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Generator

A device used to generate electricity, in which the work done to turn the coil within the magnetic field is transferred to electrical energy.

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Geostationary Orbit

An orbit of the Earth made by a satellite that has the same time period and orbital direction as the rotation of the Earth and is in the equatorial plane

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Gravitational Collapse

Inward movement of material in a star due to the gravitational force caused by its own mass. Gravitational collapse occurs in a mature star when the internal gas and radiation pressure can no longer support the stars own mass

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Gravitational Field

The region around a body in which other bodies will feel a force due to the mass of a body

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Gravitational Field Lines

Lines that show the shape of a gravitational field. The direction of a field line at a point is the direction in which a small mass would move if placed at that point

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Gravitational Field Strength

The force acting per unit mass at a point in a gravitational field

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Gravitational Potential

The work done in moving a unit mass from infinity to that point

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Hadrons

Particles consisting of a combination of quarks to give a net zero or whole number charge. Neutrons and protons are hadrons

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Half Life

The mean time taken for the activity of a source, or the number of undecayed nuclei present to halve

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Hertsprung-Russell Diagram

A luminosity-temperature graph

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Hubble's Law

States that the recessional velocity of a galaxy is directly proportional to its distance from the Earth

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Ideal Gas

A gas that has internal energy only in the form of random kinetic energy

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Ideal Gas Equation

pV=nRT

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Impedance Matching

The reduction in intensity of reflected ultrasound at the boundary between two substances, achieved when the two substances have similar or identical acoustic impedences

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Induced e.m.f

The e.m.f. produced by electromagnetic induction

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Induced Nuclear Fission

Occurs when a nucleus absorbs slow-moving neutrons and the resulting unstable nucleus undergoes a fission reaction to split into two smaller nuclei and a small number of neutrons, releasing energy

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Internal Energy

The sum of the randomly distributed kinetic and potential energies of all the atoms or molecules within a system

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Isochronous

Constant and independent of amplitude. The period of an object with simple harmonic motion is isochronous

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Isotopes

Atoms of the same element which contain the same number of protons but can have varying number of neutrons

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Kepler's Third Law

States that the square of the period of a planet orbiting the Sun is proportional to the mean radius of its orbit cubed

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Kinetic Model of Matter

States that all matter is made up of very small particles which are in constant motion. Allows explanation of the properties of matter and state changes

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Lenz's Law

States that the direction of any induced e.m.f. or induced current is in a direction that opposes the flux change that causes it

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Leptons

Fundamental particles. Electrons and Neutrinos are leptons

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Light-Year

The distance travelled by light in one year.

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Luminosity

The total energy a star emits per second

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Magnetic Field

A region around a permanent magnet or a moving charge in which another body with magnetic properties will feel a force

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Magnetic Field Lines

Show the shape and direction of a field.

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Magnetic Flux Density

A measure of the strength of a magnetic field.

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Magnetic Flux Linkage

The product of the magnetic flux through a coil and the number of turns on a coil.

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Main Sequence Star

A star in the main part of it's life cycle, where it is fusing hydrogen to form helium in its core

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Mass Defect

The difference in mass between the mass of a nucleus and the total mass of its separate nucleons

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Maxima

Regions of brightness which will be seen when the path difference between overlapping waves is equal to a whole number of wavelengths

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Mean Square Speed

The mean value of the square of velocity for a large number of gas particles moving randomly in a gas

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Moderator

A substance used in a nuclear reactor which slows down neutrons so that they have a greater chance of being absorbed by the fissile nuclear fuel.

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Mole

One mole of any substance is the amount of substance that contains as many particles as exactly 12.0g of carbon-12.

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Natural Frequency

The frequency at which a system will oscillate when undergoing free oscillations

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Neutrino

A fundamental particle with almost no mass and zero charge. Each neutrino has an antimatter partner, called an antineutrino

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Neutron Star

The remains of the core of a red super giant after it has undergone a supernova explosion. Incredibly dense and composed of mainly neutrons

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Newton's Law of Gravitation

States that the gravitational force of attraction between two point masses is directly proportional to the product of their masses and inversely proportional to the square of their seperation

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Nuclear Fusion

The process of two nuclei joining together and releasing energy from a change in binding energy

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Nucleon Number

The number of nucleons inside the nucleus of a particular atom

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Pair Production

The process of creating a particle-antiparticle pair from a high-energy photon

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Parsec

A unit of distance that gives a parallax angle of 1 second of arc, using the radius of the Earth's orbit as the baseline of a right angled triangle.

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Period

The time taken for one complete pattern of oscillation at any point, measured in seconds.

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Permittivity

A constant related to the size of the capacitance of a capacitor.

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Permittivity of Free Space

A physical constant related to the size of the force between electric charges in free space.

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Phase Difference

The fraction of a complete cycle or oscillation between two oscillating points, expressed in degrees or radians

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Photomultiplier Tube

A device used to give a pulse of electrons for each incident photon

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Piezoelectric Effect

The change in volume of a material when a p.d. is applied across its opposite faces. Alternatively, the production of an induced e.m.f. when certain crystals are placed under stress

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Planetary Nebula

An expanding, glowing shell of ionised hydrogen and helium ejected from a red giant star at the end of its life

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Positron Emission Tomography

The use of gamma photons, produced when positrons annihilate with electrons inside the body, to map out biologically active areas within the body

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Proton Number

The number of protons inside the nucleus of a particular atom

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Quarks

Components of hadrons, which have a fractional electric charge. They are believed to be fundamental particles.

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Radian

One radian is the angle subtended at the centre of a circle when the arc is equal in length to the radius of the circle

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Radiation Pressure

Outward pressure due to the momentum of photons released in fusion reactions. Acts in the direction of the energy flow

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Red Giant

A star in the later stages of its life that has nearly exhausted the hydrogen in its core and is now fusing helium nuclei. It is bigger than a normal star because its surface layers have cooled and expanded.

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Red Shift

The apparent increase in wavelength of electromagnetic radiation caused when the source is moving away, relative to the observer

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Red Super Giant

A star that has exhausted all the hydrogen in its core and has a mass much higher than the Sun

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Relative Permittivity

The factor by which the capacitance of a capacitor with that material between its plates is increased relative to the capacitance of the capacitor with air or vacuum between its plates

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Resonance

Occurs in forced oscillations when the driving frequency is equal to the natural frequency of the system being forced to oscillate

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Root Mean Square Speed

The square root of the mean square speed

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Scintillator

A material that produces many photons of visible light when struck by a high-energy photon

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Search Coil

A small, flat coil used to determine the strength of a magnetic field

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Simple Harmonic Motion

Oscillation of a body in which its acceleration is directly proportional to its displacement from a fixed point and always directed towards that fixed point

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Solenoid

A long coil of current carrying wire

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Specific Heat Capacity

The amount of energy needed to raise the temperature of 1 kg of a substance by 1 K

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Specific Latent Heat of Fusion

The amount of energy required to change the phase of 1 kg of a substance from a solid to a liquid

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Specific Latent Heat of Vaporisation

The amount of energy required to change the phase of 1 kg of a substance from a liquid to a gas

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Stefan's Law

Relates the luminosity of a star with its absolute temperature

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Stellar Parallax

The apparent shifting in position of a star viewed against a background of distant stars when viewed from different positions of the Earth, such as at different positions of the Earth's orbit around the Sun

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Strong Nuclear Force

A force that acts between nucleons and holds the nucleus together against the electrostatic repulsion of the protons

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Supernova

A huge explosion produced when the core of a red super giant collapses

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Thermal Equilibrium

A situation in which there is no net heat flow between two objects in contact with each other

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Thermodynamic Scale of Temperature

A temperature scale which is independent of the properties of any specific substance

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Time Constant

The time taken for the change remaining on a capacitor to decrease to about 37% of its initial value

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Tracer

A radioactive substance either ingested by, or injected into, a patient. It emits gamma photons to be detected by a gamma camera

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Transducer

A device, such as a microphone, which converts a non electrical signal into an electrical signal

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Transformer

A device that can either increase or decrease the size of an alternating voltage with little loss of power

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Transmission Diffraction Grating

A glass surface with a large number of very fine parallel grooves or slits, which is used to produce optical spectra by diffraction of transmitted light

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Ultrasound

Longitudinal waves above the upper limit of the audible range, with frequencies greater than 20 000 Hz

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Unified Atomic Mass Unit

Defined as one-twelfth of the mass of a carbon-12 atom

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Velocity Selector

A device using perpendicular magnetic and electric fields to select charged particles travelling at a specific velocity, which leave the region of crossed fields without being deflected

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Weak Nuclear Force

A force felt by both quarks and leptons. It can change quarks from one type to another or leptons from one type to another and is responsible for beta decay

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Weber

One weber is the magnetic flux when a magnetic field of flux density one tesla passes at right angles through an area of one square metre

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White Dwarf

The end product of a low mass star, when the outer layers have dispersed into space. Very dense with a high surface temperature and low luminosity

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Wien's Displacement Law

Used to estimate the peak surface temperature of a star from the wavelength at which the star's brightness is maximum

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## Other cards in this set

### Card 2

#### Front

The acceleration of a body falling under gravity

#### Back

Acceleration of free fall

### Card 3

#### Front

The rate of change of velocity measured in metres per second squared.

#### Back

### Card 4

#### Front

The degree to which a value obtained by an experiment is close to the true value

#### Back

### Card 5

#### Front

A device used to measure electric current, connected in series with the components

#### Back

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