# Physics Key Words

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Kinetic Energy
Energy a body has because of its movement
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Kinetic Theory
Theory describing movement of molecules in gases, liquids and solids
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Law of Conservation of Energy
Energy cannot be created or destroyed
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Magnetic Field
The area of effect of a magnet (or the Earth) indicated by lines of force surrounding the magnet (or the Earth)
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Mains Electricity
Electricity supplied centrally to households and businesses
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Mass
The quantity of matter in an object
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Mass number
The number of protons and neutrons in an atomic nucleus
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Neutron
A subatomic particle found in the nucleus; has no charge
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Non-renewable Energy Source
An energy source that can't be replaced as fast as it is used
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Nuclear Fission
The splitting of atomic nuclei
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Nuclear Fusion
Process whereby nuclei of small atoms join to make a larger nucleus, releasing energy
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Period (of wave)
Inverse of frequency
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Potential Difference (Voltage)
The difference in potential between two points in an electrical circuit; the energy transferred in a circuit by each coulomb of charge; measured in volts (V)
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Power
The rate of doing work; measured in watts (W)
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Pressure
The effect of force spread out over an area; pressure is equal to force divided by area. Pressure difference in a fluid = density x g x height difference
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Primary Energy Source
Energy source directly from Earth e.g. Coal
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Proton
A subatomic particle found in the nucleus; has a charge of +1
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Substance that emits radiation from its atomic nuclei
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Reflection
Change in direction of a wave at a boundary between two media
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Refraction
Change in direction of a light ray as it passes from one medium to another and changes speed
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Refractive Index
A measure of a medium's ability to bend light due to slowing the light down
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Renewable
Energy sources that will not run out
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Residual Current Circuit Breaker (RCCB)
Automatic device for breaking a circuit; based on detecting a difference in current between the live and neutral wires
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Resistor
An electrical device that resists the flow of an electrical current
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Resistance
How hard it is to get a current through a component at a particular potential difference; measured in ohms
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Risk
The danger (normally to health) associated with a procedure, action or event
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Sankey Diagram
An energy transfer diagram where the widths of the arrows are proportional to the amount of energy used
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Speed
The rate at which an object moves
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Terminal Velocity
Maximum velocity of a falling velocity
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Thermistor
A resistor whose resistance varies with temperature
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Thinking distance
The distance that a car travels whilst the driver reacts and starts to brake
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Total Internal Reflection
Complete reflection of a light or infrared ray back into a medium
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Transfer
Moving energy from one place to another
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Transformer
An electrical device that changes the voltage of electrical circuits
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Unstable nuclei
Nuclei that can decay
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Velocity-time graph
A graph showing velocity against time
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Voltage (potential difference)
The difference in potential between two points in an electrical circuit; the energy transferred in a circuit by each coulomb of charge; measured in volts (V)
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Wavelength
The distance between corresponding points on two adjacent disturbances
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Analogue
Signal varies continuously in amplitude/frequency
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Conservation of Momentum
The total momentum before and after a collision is the same
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Diffraction
The spreading out of a wave as a result of passing an obstacle through a gap
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Digital
Signal that uses only 0s and 1s
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Earthing
Connecting appliance to Earth using Earth wire
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Gas
State of matter where particles are very spread out
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Law of Moments
When the total clockwise motion and total anticlockwise motion of an object are equal
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Liquid
State of matter where particles are less spread out than in a gas but more than in a solid
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Moment
A turning force; the product of the force and the perpendicular distance from the force to the pivot point
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Momentum
The fundamental quantity that is a measure of the state of motion of an object; product of mass and velocity; p = m x v ; units of kg m/s
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Noise
Unwanted frequencies in a signal that can distort it
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Resultant Force
The combined effect of all the forces acting on an object
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Scalar quantity
A quantity where there is only one size
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Solid
The state of matter, where the particles are very close together
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Static Electricity
Build-up of charge on a substance
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Vector Quantity
A quantity where both size and direction are known
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## Other cards in this set

### Card 2

#### Front

Theory describing movement of molecules in gases, liquids and solids

Kinetic Theory

### Card 3

#### Front

Energy cannot be created or destroyed

### Card 4

#### Front

The area of effect of a magnet (or the Earth) indicated by lines of force surrounding the magnet (or the Earth)

### Card 5

#### Front

Electricity supplied centrally to households and businesses