# OCR Physics B (Advancing Physics) Yr 2 Glossary

Fully inclusive collection of the definitions for the 2nd Yr. collected from the textbook, revision guide and checked against past mark schemes.

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- Created on: 27-05-18 13:25

Absolute Luminosity

The brightness a star world have at a standard distance of 10 parsec

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Absolute Zero

The zero of the thermodynamic temperature at 0K or -273 degrees C. Particles of ideal gas have no energy at this temperature

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Absorbed Dose

The number of joules of energy absorbed from ionizing radiation per kilogram of tissue (Unit = grays, Gy)

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Activation Energy, E

The minimum energy required for a given process to occur

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Activity

The number of nuclei in a radioactive source that decay per second (Unit= Bq)

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Alternating Current

A current, alternating sinusoidally, produced by an alternating p.d. in a circuit.

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Amplitude

The maximum displacement of an oscillator from its equilibrium position

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Angular Frequency

The angle moved per second (Unit= radians)

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Anti-Particle

The counterpart to a particle which has the same rest energy and is equal but oppositely charged

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Armature

The rotating part of an electric motor, which carries the coil

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Astronomical Unit

The mean distance between the Earth and Sun

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Atomic mass unit, u

One twelfth of the mass of an atom of carbon-12

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Avogadro constant

The number of particles in a mole of substance

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Back e.m.f.

An e.m.f. generated by a spinning motor that opposes the p.d. driving the motor and limits its speed

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Background radiation

Radiation that is detectable from the environment which is not involved in an experiment

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Big Bang Theory

The probable origin of the universe in a very hot, dense state from which it has expanded and cooled

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Binding Energy

The energy required to break a nucleus into its individual nucleons

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Boltzmann Factor

The proportion of particles in a substance which have energy above the activation energy required for a given reaction

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Boyle's Law

The pressure of an ideal gas is inversely proportional to volume, at a constant temperature. pV=constant

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Capacitance

The charge separated per volt of a capacitor

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Chain reaction

A reaction is which the products of a reaction go on to start one or more further reactions

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Charles' Law

The volume of an ideal gas is proportional to the temperature, at a constant pressure. V/T=constant

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Commutator

A switching mechanism that reverses the connections to the coil of an electric motor to maintain its direction of motion

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Cosmetic background radiation

Microwave radiation that permeates the entire universe and was created during the Big Bang. Its wavelength has increased due to being stretched over time as the universe expands.

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Cosmological Red-Shift

The red shift of light from very distant galaxies that is caused by the wavelength of the light being stretched as the universe has expanded.

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Coulomb's Law

The force between two charged spheres is directly proportional to each of the charges and inversley proportional to the square of the distance between the centers of the charges.

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Count Rate

The number of particles of ionizing radiation emitted from a radioactive sample that are detected by the measuring system per second. It is less than, but proportional to, the activity.

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Critical damping

Reduction of simple harmonic motion in which the oscillator stops at the equilibrium position without completing a cycle

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Damping

The action of forces such as friction to reduce the amplitude of an oscillator due to energy loss from the system

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Decay constant

The probability that a nucleus will decay during a time interval of 1 second (Unit= S^-1)

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Diffusion

The slow intermingling of gases or liquids, due purely to the random motion of the particles

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Doppler Shift

A change in observed wavelength due the relative motion of source and observer

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Effective Dose

The product of the absorbed dose and the quality factor of the ionizing radiation that has been absorbed. (Unit= sieverts, Sv)

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Dynamo

An older term for an electrical generator, now sometimes used to refer to a d.c.generator

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Eddy Current

Electrical currents induced in the core of a transformer by the changing flux linkage within the core. The currents oppose the change in flux that caused them causing work to be done and so energy loss in the core.

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Einstein's 1st Postulate

Physical behavior cannot depend on any 'absolute velocity'. Physical laws must take the same form for all observers, no matter what their state of uniform motion in a straight line

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Einstein's 2nd Postulate

The speed of light is a universal constant.

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Electric Field

A region surrounding an electrical charge where another electrical charge would experience a force

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Electric Field Strength

The magnitude and direction of the force per unit charge at any given point in an electric field

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Electrical Potential

The potential electrical energy per unit of charge in and electric field given as the work done to move the unit of charge from infinity to that postition

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Electrical Potential Energy

The potential energy of a charge in an electric field given as the work done when moving the charge from an infinite distance to its position within the electric field

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Electrical permittivity of free space

A fundamental electrical property of free space

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Energy

A measure of the capacity of a body or system to do work

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Equilibrium Position

The position of an oscillator on which no net force is acting

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Equipotential Surface

A continuous surface joining points of the same potential in a three dimensional field

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Exponential change

Difference in values has a constant ratio property where the value will change by the same ratio in equal time

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Faraday's Law

The induced e.m.f. will produce a current which opposes the rate of change of flux linkage responsible for the induction (eddy currents)

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1st Law of Thermodynamics

The change in internal energy of a system is the sum of the work done on the system and the energy transferred thermally into it

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Flux Linkage

The product of the number of turns of wire in a coil and the flux that is induced per coil

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Forced oscillation

An oscillation driven by the action of a periodic driving force

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Free oscillation

An oscillation due to the action of a restoring force without any dampening or driving forces

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Generator

An electromagnetic machine that uses rotation to produce the flux changes needed to induce an e.m.f.

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Gluon

The exchange particle that mediates the strong nuclear force

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Gravitational Field

The region surrounding a mass where another mass would experience a force

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Gravitational Field Strength

The magnitude and direction of the force per unit mass at a given point in a gravitational field

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Gravitational potential

The gravitational potential energy per unit mass at a given position in a gravitational given as the work done to move the unit mass from infinity to its position in the gravitational field

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Gravitational Potential Energy

The work done to move a mass from infinity to its position in the gravitational field

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Hadron

A particle composed of two or three quarks

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Half-life

The time required for the number of nuclei in a sample to reach half the original value

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Half-thickness

The thickness of absorber needed to halve the number of photons that can pass through on average

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Heavy Dampening

Reduction of simple harmonic motion in which the oscillator returns to the equilibrium position much more slowly than a lightly of critically damped oscillator

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Hertzsprung-Russell diagram

A logarithmic plot of the luminosity of stars against their surface temparature

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Hubble's Law

The recessional velocity at which a galaxy is moving away from the earth is proportional to its distance from earth. Provides evidence for the big bang since all galaxies must have started at a single point

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Ideal gas

A gas in which there is no intermolecular interaction and the molecules occupy negligible volume

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Induction

The creation of an e.m.f. across a circuit when the magnetic flux in the circuit is changed

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Internal energy

The energy within a system allowing it to do work or transfer energy thermally / The sum of the kinetic and potential energy of the particles within a system

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Ionic bond

A strong bond between ions due electrostatic attraction, bond are localized and directional

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Ionisation

Removal of an electron from, or addition of an electron to, an uncharged atom or molecule resulting in the formation of an ion

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Ionisation energy

The energy that must be supplied to a neutral atom or molecule in order to ionize it

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Ionized Gas

A gas in which some atoms have lost electrons to become positive ions

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Isotope

Forms of the same element where they have the same proton number but different neutron numbers

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Iteration

A repeat of a mathematical operation

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Laminations

Insulating between thin layers of core in a transformer to reduce the area that eddy currents can form over which reduces the size of the currents which helps to reduce the energy lost when by the currents opposing the changing flux linkage

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Lenz's Law

The direction of an induced e.m.f. is always such as to act against the change that caused the induced e.m.f.

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Lepton

A group of fundamental particles (e.g. electrons and neutrinos)

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Lidar

Light detection and ranging. Finding the distance to a remote object using the delay in return of a pulse of light.

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Light Dampening

Reduction of simple harmonic motion in which the maximum displacement of the oscillator is reduced in each oscillation but the time period of the oscillation is roughly constant

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Light-year

The distance travelled by light in 1 year

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Magnetic circuit

Analogous to an electric circuit, an arrangment whereby flux between magnetic poles is carried by a suitable magnetic material between poles

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Magnetic Field

A region surrounding a magnet in which a moving charge would experience a force

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Magnetic Flux Density

A measure of the strength of a magnetic field (Unit= Tesla, T)

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Mass Defect

The difference between the mass of a nucleus and the total mass of the individual nucleons

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Metallic Bond

A strong bond between the positive ions of metal atoms which are held together in a lattice by a sea of delocalized electrons, bonds are non-directional and delocalized

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Moderator

A material (often water) used to slow down neutrons in a fission reactor to increase the probability of successful further reactions due to collisions

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Molar mass

The mass of 1 mole of a substance

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Natural Frequency

The frequency of a free oscillator

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Neutrino

An uncharged lepton of insignificant mass, very low interaction

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Neutron

An uncharged hadron composed of 2 down an 1 up quark, udd

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Nuclear Fission

The splitting of a heavy nucleus to form lighter nuclei

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Nuclear Fusion

The fusion of two light nuclei to form a heavier nucleus

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Nucleon

Particles found in the nucleus of an atom (protons and neutrons)

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Nucleon number

The number of protons and neutrons in the nucleus of an atom

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Nucleus

The central, relatively massive core of an atom

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Overdampening

Reduction of simple harmonic motion in which the oscillator stops at the equilibrium position without completing a cycle but in much longer time that critical dampening

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Parallax

The apparent shift in position of near objects against the background of further objects when the observer moves

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Parsec, pc

The distance at which a star would have a parallax angle from earth of 1

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Particle Accelerator

A device using electrical fields to accelerate charge particles

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Pauli exclusion principle

No 2 identical fermions (electrons, protons and neutrons) can share the same quantum state: e.g. opposite spin on electrons. Explains why the matter does not collapse into itself.

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Pendulum

A mass (bob) on the end of a spring that can demonstrate simple harmonic motion

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Permeance

A measure of how easily flux lines are set up in a magnetic circuit.

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Permeability

A measure of the number of flux lines that are set up per unit area for a given material and e.m.f.

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Positron

The antiparticle counterpart of an electron

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Pressure Law

The pressure in an ideal gas is proportional to the temperature for a constant volume. P/T= constant

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Proton

A positively charged hadron composed of 2 up and 1 down quark, uud

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Proton Number

The number of protons in the nucleus of an atom

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Quark

The fundamental particle that makes up hadrons

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Radar

Radio detection and ranging. Finding the distance to a remote object using the delay in return of a pulse of electromagnetic radiation.

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Radioactive decay

The release of particles by the nuclei of atoms of unstable elements

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Radioactivity

The phenomenon whereby unstable nuclei change, emitting ionizing radiation

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Random Walk

The random movement of a single molecules during diffusion due to repeated collisions with other molecules. Total displacement will be the square route of N steps of constant distance

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Random

A situation in which an event occurs by chance and is not effected by any external factors (e.g. temperature, pressure or other events)

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Red-shift

The shift of spectral lines towards the red end of the colour spectrum caused by the doppler shift of light from galaxies which are moving away from the earth

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Resonance

The effect produced when the driving frequency is close to or matches the natural frequency of an oscillator resulting in larger amplitude oscillations

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Restoring force

The force acting towards the equilibrium position of an oscillator which causes it to accelerate in the opposite direction to the motion of the oscillator

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Risk of radiation

The probability of developing cancer due to exposure to ionizing radiation per sievert of effective dose

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Root mean square speed

The square root of the mean square speed. (all speeds squared, mean value taken, mean value rooted)

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Rotor

The rotating part of an electric motor or generator

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Scattering

The deflection of accelerated particles due to interaction with nuclei or with other particle

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2nd Law of Thermodynamics

The total entropy never decreases. (Molecular collisions always redistribute energy not lose it)

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Simple Harmonic Motion

When the acceleration of a system at any instant is proportional to its displacement from the equilibrium position at that instant and acts in the opposite direction to this displacement towards the equilibrium position

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Solenoid

A long, current carrying coil which acts as an electromagnet

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space-time diagram

A representation of the paths of objects moving through space and time. Time on the y-axis (seconds, s) and distance on the x-axis (light-seconds, x/c)

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Specific Thermal Capacity, c

The increase in internal energy required to raise the temperature of 1kg of andy given material by 1K

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Standard Candle

A star of known absolute luminosity that can be used as a comparative measure for other stars

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Statistical mechanics

The study of how the behavior of matter and energy is governed by statistics dealing with random distributions

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Stator

The stationary part of an electric motor or generator

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Strong interaction

A fundamental force that holds nuclei together

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Strong nuclear force

The force that holds nuclei together in the nucleus

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Tesla

The unit for flux density, the force per unit current per length of a conductor perpendicular to the lines of magnetic flux

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Time constant,

The product of RC, the time for the charge on a capacitor to reduce to 37% of its original value

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Time period

The time for one complete oscillation of an oscillator

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Transformer

An electromagnetic machine that transforms voltages by inducing e.m.f. without physical movement

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Van der Waal forces

Weak intermolecular forces between molecules caused by the interaction of instantaneously induced dipoles of the molecules

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Worldline

A line on a space time diagram representing the path of an object through space and time. World lines for electromagnetic pulses are at 45 degrees

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## Other cards in this set

### Card 2

#### Front

The zero of the thermodynamic temperature at 0K or -273 degrees C. Particles of ideal gas have no energy at this temperature

#### Back

Absolute Zero

### Card 3

#### Front

The number of joules of energy absorbed from ionizing radiation per kilogram of tissue (Unit = grays, Gy)

#### Back

### Card 4

#### Front

The minimum energy required for a given process to occur

#### Back

### Card 5

#### Front

The number of nuclei in a radioactive source that decay per second (Unit= Bq)

#### Back

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