# Physics

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Pressure (equation)
Pressure = force / area
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Pressure unit
Pa or N/m2
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Increase in pressure (equation)
Height x gravitational field strength x density
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Moment
A turning force such as trying to open or close a door or using a spanner
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Moment (equation)
Moment = force x distance from pivot
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Lever
Can be used to apply a force which turns something around a pivot
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Equilibrium
For a beam to balance the total clockwise moment must equal the total anti-clockwise moment
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Gears
Wheels with teeth that’s slot together, which can be used to increase the power of a turning force
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Density
A measure of how closely packed particles are in a material
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Density (equation)
Mass / volume
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Solids
Regular particle arrangement, cannot be compressed, don’t flow, can’t change shape
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Liquids
Regular particle arrangement but can flow, cannot be compressed, can change shape
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Gases
Irregular particle arrangement - spread out, can be compressed, can flow, can change shape
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Evaporate
When a liquid substance is given enough energy it will turn into a gas
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The latent heat of fusion
The energy needed to melt 1kg of ice
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Latent Heat of Fusion (Equation)
Amount of energy / mass
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Heat
The name for a type of kinetic energy possessed by particles
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Temperature
The measure of the average heat per particle or how hot or cold an object is
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Conduction
As a substance is heated, the particles begin to vibrate as they get more energy. These vibrations are passed on to the next particle and the next, making the heat energy travel through the substance
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Convection currents
As particles are heated they expand and so become less dense, making them rise. The higher they go, the cooler it is as they travel away from the heat source so they contract, becoming denser and fall again.
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The suns heat travels to the Earth by infrared waves
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Insulation
Reduces heat energy transfer
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Electrical energy (equation)
Power x time
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Specific Heat Capacity
The amount of energy needed for 1kg of a material to increase in temperature by 1*C
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Specific Heat Capacity (Equation)
Energy / (mass x temperature change)
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Specific Heat Capacity (Units)
J/kg*C
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Specific Heat Capacity of water
4200J/kg*C
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Energy
Allows things to happen
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Kinetic energy
Anything moving
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Thermal energy
Any object - the hotter it is, the more energy it has in this store
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Chemical energy
Anything that can real ease energy by a chemical reaction
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Gravitational potential energy
Anything in a gravitational field ie. anything that can fall
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Elastic potential energy
Anything stretched, like springs and rubber bands
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Electrostatic energy
E.g. two charges that attract or repel each other
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Magnetic energy
E.g, two magnets that attract or repel each other
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Nuclear energy
Atomic nuclei release energy from this store in nuclear reactions
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Energy pathway
A route along which energy can be transferred or a method by which energy is exchanged between stores
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Mechanical pathway
A force acting on an object e.g. pushing
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Electrical pathway
A charge doing work e.g. charges moving around a circuit
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Heating pathway
Energy transferred from a hotter object to a colder one e.g. heating a pan on a hob
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Energy transferred y waves e.g. energy from the sun reaching Earth by light
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Law of conservation of energy
Energy cannot be created or destroyed just moved from store to store
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Sankey Diagram
Shows the efficiency of a device at transferring energy
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Energy efficiency (equation)
Amount of energy in useful store / amount of energy in starting store
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Work done (equation)
Force x distance moved
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Power (equation)
Work done / time taken
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Transverse waves
E.g. Light. Perpendicular particle movement.
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Longitudinal waves
E.g. sound. Parallel particle movement, spread out then close.
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Rest position/equilibrium
Where the particles would be if there was no wave
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Amplitude
Maximum displacement from the rest position
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Wave length
Length of a complete wave
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Time period
Time for one wave to pass a point
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Frequency
Number of waves per second
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Wave speed (equation)x2
Wavelength / time period or wavelength x frequency
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Refraction
When there is a change in density, the wave bends as it passes through the medium
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Virtual images
formed from the apparent divergence of light rays from a point, as opposed to an image formed from this actual divergence
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Ultrasound
A sound over 20000Hz
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Infrasound
A sound below 20Hz
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Frequency (equation)
Number of waves / number of seconds
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How many forces does it take to change the shape of an object?
Two
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Hooke’s Law
The strain in a solid is proportional to the applied stress within the elastic limit of that solid
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Spring constant (equation)
Force / extension
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Renewable energy resources
Resources that will not run out
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Non renewable energy resources
Resources that will eventually run out
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Wind power
Power obtained by harnessing the energy of the wind, using turbines
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Solar power
Power obtained by harnessing the energy of the suns rays using solar panels or cells
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Hydroelectric power
Water is stored behind a dam in a reservoir, the water runs down the pipes to turn the turbine, and produce electricity
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Wave power
Power obtained by harnessing the energy produced by waves at sea
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Tidal power
Obtained from changing sea levels
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Bio-mass energy
Biomass is burnt to generate electricity
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Geothermal energy
Heat energy produces by the internal heat of the Earth
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Which way do electrons flow in a circuit?
- to + terminal
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Which way is the conventional flow in a circuit?
+ to - terminal
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Resistance
Measures how hard it is for the current to get through a material
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Current
The rate of flow of charge
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Current (equation)
Charge / time
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Current (units)
A - Amps
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Series circuit
Connected on the same path
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Parallel circuit
Where there are different paths to take
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Voltage
How much energy the charge transfers
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What is another name for voltage?
Potential difference
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Voltage (equation)
Energy / charge
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Voltage (units)
V - volts
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Charge (units)
C - coulombs
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Resistance (equation)
Voltage / current
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Resistance (units)
Ohm
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Ohm’s Law
States that current and voltage are directly proportional
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I-V graph - Ohmic graph
Obeys ohm’s Law - current and voltage are directly proportional
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I-V graph
Current voltage graph
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I-V graph - Lamp
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I-V graph - Diode
Almost no current flows if the voltage is applied in the reverse direction. A current flows in the forward direction whenever the voltage is more than about 0.6V.
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Diode
Allows a current to flow only one way
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Uses of diodes
Protecting equipment, switching in stand by batteries and rectification
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Ammeter (ES)
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Power pack (ES)
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Motor (ES)
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Cell (ES)
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Voltmeter (ES)
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Light dependant resistor (ES)
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Open switch (ES)
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Resistor (ES)
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Bulb (ES)
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Fuse (ES)
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Variable resistor (ES)
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Diode (ES)
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Closed switch (ES)
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Thermistor (ES)
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Heater (ES)
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Electrical power (equation)x2
Current x voltage or current squared x resistance
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Speed (equation)
Distance/time
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Acceleration (equation)
Change in velocity / time taken
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Weight (equation)
Mass x gravitational field strength
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Momentum (equation)
Mass x velocity
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Change in gravitational potential energy (equation)
Mass x gravitational field strength x change in vertical height
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Kinetic energy (equation)
1/2 x mass x speed squared
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Vector quantity
Has both a size and direction
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Scalar quantity
Has only a size, no direction
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Acceleration (units)
m/s squared
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The distance traveled is the area under the line on what type of graph?
Velocity - time graphs
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Change in GPE, KE, and elastic energy are equal to...
...work done
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Field
A place where an electrical charge will feel a force
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Discharging
Releasing or neutralising the electric charge of an electrical object
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Earthing
Connecting an electrical device to the ground
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Fission
Splitting of heavy nuclei
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Chain reaction
A reaction which grows very quickly
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Concrete shield
The whole reactor is shelled in steel and concrete to absorb the dangerous gamma rays
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Heat exchanger
The heat boils water to make high pressure steam, which turns the turbine
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Fuel rods
Where the fission happens
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Moderator
Slows down the fission neutrons so they work more efficiently
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Coolant
Carries the heat from the reactor to the heat exchanger
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Control rods
Limit the fission by absorbing neutrons
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Fusion
The joining of light nuclei
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Free body diagrams
Show the forces on an object
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Resultant force
The sum of the forces
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Newton’s First Law
States that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force
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Newton’s Second Law (equation)
Resultant force = mass of object x acceleration
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Newton’s Third Law
All forces in the universe occur in equal but oppositely directed pairs
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Upthrust
the upward force that a liquid or gas exerts on a body floating in it
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Centripetal Force
a force that acts on a body moving in a circular path and is directed towards the centre around which the body is moving
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Alternating current
Current flows one way around the circuit and then back again in the opposite direction - mains electricity
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Direct current
Current flows one way only around the circuit - cells
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What voltage is mains electricity supplied at?
230V
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What frequency is mains electricity?
50Hz
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Fuse
If a fault occurs in a circuit, the fuse melts before anything else is damaged
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Circuit breakers
Fuses which can be reset and act more quickly and reliably than fuses
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The Earth Wire
Provides a conducting oath from the metal case to the ground
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The Live Wire
Alternates in potential between +325V to -325V
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The Neutral Wire
At or near 0V and conducts an electrical current whenever the appliance is switched off
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Fuse rating
The maximum current that the fuse can carry without melting - 3A, 5A OR 13A
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How big is an atom?
0.1 to 0.5nm
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Alpha particle
Contain 2 protons and 2 neutrons
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Beta particle
Same as an electron
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Gamma Ray
Electromagnetic wave
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Decay equation - Alpha
When alpha is emitted the top number (atomic/proton number) decreases by 4 and the bottom number (nucleon number) decreases by 2
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Decay equation - Beta
When beta is emitted a neutron turns into a proton and a beta - the bottom number (nucleon number) stays the same and the top number (proton number) increases by 1
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Decay equation - Gamma
Stays the same
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Positron
Has the same mass as an electron but a charge of +1 instead of -1
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Properties of Alpha
+2 charge, small deflection, highly ionising, weakly penetrating
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Properties of Beta
-1 Charge, large deflection, moderately ionising and moderately penetrating
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Properties of Gamma
No charge, not deflected, weakly ionising, strongly penetrating
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The radiation around us all of the time
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Decay
When a nucleus emits radiation to become stable
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The number of particles that decay each second
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Bq - bequeral
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Count rate
The number of decays counted for a specific time
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Electromagnetic spectrum
the range of wavelengths or frequencies over which electromagnetic radiation extends
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What are the 7 components of the electromagnetic spectrum?
Radio waves, microwaves, infrared, visible light, ultra violet, x rays, gamma rays
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Excitation
When an electron jumps from one energy level to the next because it has absorbed the right amount of energy
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Dexcitation
When an electron jumps down from one energy level to the next and they give out energy
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What determines the colour of a star
Temperature - blue is the hottest, red the coolest
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Total internal reflection
the complete reflection of a light ray reaching an interface with a less dense medium when the angle of incidence exceeds the critical angle
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Fibre optics
Used to guide light from one place to another
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Specular
Reflection from a smooth surface at a definite angle
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Diffuse (reflection)
Reflection from a rough surface at multiple angles
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Differential absorption
When a surface absorbs some wavelengths it changes the colour
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Convex lens
When parallel rays of light pass through a convex lens the refracted rays converge at one point
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Concave lens
It spreads out light rays that have been refracted through it
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Magnification (Equation)
Image size / actual size
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Real image
Where the light rays actually travel to the image
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Momentum
A measurement of how hard it is to stop something or to change the motion o something
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Magnet
Will attract magnetic materials and attract or repel another magnet
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Poles
Two ends of a magnet which give different forces
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Fields
The area around a magnet where a force is
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Electromagnetism
Materials become magnetic when a current is passed through it
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Uniform fields
Field lines are parallel and equally spaced
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Momentum (equation)
Momentum = mass x velocity
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Momentum (units)
Kgm/s
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Change in momentum (equation)
Force x time
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Thinking distance
How far you travel while reacting
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Braking distance
How far you travel once the brakes are pressed to when you stop
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Stopping distance (equation)
Thinking distance + braking distance
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Boyle’s Law
the pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature
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Absolute zero
The point where there is no pressure or heat energy and therefore no particle movement in a substance. This happens at -273*C.
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Where does the Kelvin scale start?
-273*C
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Telescopes
The lenses are big so more light enters so we can see more objects
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Where is an asteroid belt located in our solars system?
Between Mars and Jupiter
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Weight (equation)
Mass x gravity
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The Doppler Effect
The change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source
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Red shift
Proves that the universe is expanding as the wavelengths are shifted towards the red end of the spectrum
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What does CMB stand for?
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Opposes the Big Bang theory and says that new matter is being created to fill in the gaps made form expansion
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## Other cards in this set

Pa or N/m2

Pressure unit

### Card 3

#### Front

Height x gravitational field strength x density

### Card 4

#### Front

A turning force such as trying to open or close a door or using a spanner

### Card 5

#### Front

Moment = force x distance from pivot