# P1 Definitions

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Temperature
Measure of how hot or cold an object is
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Heat
Form of energy, or a flow of energy from hotter objects to colder ones
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Thermogram
Image taken by an infrared camera that shows how much infrared radiation is being emitted by a body
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Specific Heat Capacity
Amount of energy needed to increase the temperature of 1kg of a material by 1 degrees Celcius
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Change of state
Changing from one physical state to another, eg from a solid to a liquid or a liquid to a gas
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Specific Latent Heat
Amount of energy needed to change the state of 1kg of a substance
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Fusion
Melting (not to be confused with nuclear fusion)
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Vaporisation
Boiling and evaporating into a gas
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Intermolecular bond
Bond between particles of a substance
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Conduction
One way of transferring energy by vibrations being passed on from one particle to another
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Thermal conductor
Material that conducts heat well
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Thermal insulator
Material that does not conduct heat well
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Free electrons
Electrons that are free to move through a substance
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Fluid
A liquid or a gas
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Convection
How thermal energy is transferred by the movement of particles in fluids
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Convection current
The movement of particles by convection when heat energy is transferred
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Form of electromagnetic radiation that you can feel as heat. It has a shorter wavelength than microwaves but a longer wavelength than visible light
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Emit
To give out
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Medium
Any substance that a wave passes through eg air, water, metal
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Heat source
Where the heat comes from
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Sink
Colder surroundings around a heat source
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Payback time
Time taken to recover the amount of money paid out in making a change from the resultant savings in energy bills
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Cost-effective
Describes when the cost of making a change is low in relation to the resultant savings in energy bills
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Sankey diagrams
Diagram that shows all the energy transfers taking place in a device
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Efficiency
Percentage of energy transferred by a device that is useful
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Crest
The top part of a wave where its displacement is at a maximum
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Trough
The bottom part of a wave where its displacement is at a maximum
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Oscillation
Back and forth motion that repeats over and over again
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Transverse Wave
Wave whose vibrations are at right angles to the direction of wave motion
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Amplitude
The maximum displacement of a wave or oscillation (the maximum height of a wave from the crest to the middle)
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Wavelength
Distance from one crest of a wave to the next crest
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Frequency
The number of oscillations per second for a vibration
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Wave equation
The speed of a wave equals its frequency multiplied by its wavelength
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Electromagnetic wave
Wave that has oscillating electric and magnetic fields at right angles to its direction in motion
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Vacuum
Region that contains no atoms or other particles. Not possible to create in practice, but outer space gets close
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Reflection
Occurs when waves bounce off objects
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Law of reflection
The angle of incidence is always equal to the angle of reflection, even if the surface is really rough
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Refraction
Change of speed and direction of a wave when it passes from one medium to another
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Diffraction
Spreading out of waves when they pass through a gap or around an obsticle
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Total Internal Reflection
When a wave travelling inside a denser medium reflects off the boundary with another medium, and so stays inside the original material
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Critical angle
Smallest angle of incidence for which Total Internal Reflection takes place
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Optical fibre
A fine glass tube designed so light can travel through it by Total Internal Reflection
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Endoscope
A medical instrument which uses optical fibres to produce an image of the inside of a patient
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Morse code
Digital code that uses long and short bursts of sound or light to represent letters of the alphabet
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Laser
Source of high intensity light with a single frequency and direction
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Phase
Waves that are in step with each other. Their crests line up with other crests
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Monochromatic
Describes a wave that has just one value for its wavelength. Monochromatic light waves contain only one colour
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Microwave
Wave that fits between radio waves and infrared in the electromagnetic spectrum
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Line of sight
Straight line path followed by light from an object to an observer
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Analogue
Describes a signal which can have an unlimited number of values
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Digital
Describes a signal that can have only one or two values; on(1), or off (0)
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Multiplexing
A technique used to transmit several digital signals at once
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Noise
Random signal with no meaning
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Radio broadcasts the transmit information as a digital signal
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Wireless communication
Use of electromagnetic waves (usually radio waves) to carry information from one place to another
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Aerial
Piece of metal the absorbs radio waves to produce an alternating current
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Ionosphere
Layer of ionised particles in the upper atmosphere, on the edge of space
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Seismic waves
Waves in the Earth's crust caused by sudden changes in the arrangement of the rocks
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P-wave
Seismic wave whose oscillations are in the same direction as the direction of travel. Sometimes called pressure, primary or push waves
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S-wave
Seismic wave whose oscillations are at right angles to the direction of travel. Sometimes called secondary, shear or shake waves
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Seismometer
Device that records seismic waves, often as a displacement-time graph on a piece of paper
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Ultraviolet
Part of the electromagnetic spectrum between X-rays and visible light
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Sun protection factor
Measure of how much longer a sun cream allows you to sunbathe safely
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Ozone layer
Layer of ozone gas high up in the atmosphere. It is a strong absorber of ultraviolet light from the Sun
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## Other cards in this set

### Card 2

#### Front

Form of energy, or a flow of energy from hotter objects to colder ones

Heat

### Card 3

#### Front

Image taken by an infrared camera that shows how much infrared radiation is being emitted by a body

### Card 4

#### Front

Amount of energy needed to increase the temperature of 1kg of a material by 1 degrees Celcius

### Card 5

#### Front

Changing from one physical state to another, eg from a solid to a liquid or a liquid to a gas