Physkeywords

	A
	A	short for amperes
	absorber	a surface that soaks up the energy from the waves or radiation that strike it
	a.c.	short for alternating current
	acid rain	rain that is more acidic that usual because of dissolved sulphur dioxide or nitrogen oxides
	air resistance	the force of friction on an object that moves through the air
	alpha (a) radiation	one of the three types of radiation that radioactive substances can give out (emit)
	alternating current	a.c. for short; an electric current that constantly changes direction
	ammeter	this is used to measure electric currents
	amperes	A for short; the size of an electric current is measured in units called amperes
	amplitude	the size of the disturbances that make up waves
	armature	the part that turns round in an electric motor
	artificial satellite	a satellite that humans have put into orbit
	atoms	all substances are made of atoms; atoms have a nucleus that is made of protons and neutrons and is surrounded by electrons
	attract, attraction	the force that pulls magnetised or electrically charged objects together
	axis	the Earth spins on its axis every 24 hours
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	B
	background radiation	the radiation from radioactive sources that is around us all the time
	battery	several electrical cells joined together
	beta (b) radiation	one of the three types of radiation that radioactive substances can give out (emit)
	billion	1,000,000,000 or one thousand million
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	C
	carbon dioxide	a gas produced when fuels burn; carbon dioxide in the atmosphere helps keep the Earth warm (greenhouse effect); too much carbon dioxide in the atmosphere makes the Earth warmer (global warming)
	cell	this uses chemicals to produce an electric current; connecting cells together makes a battery
	CHP	combined heat and power; a CHP power station makes use of heat that would otherwise be wasted, to heat buildings
	circuit breaker	this protects an electric circuit by switching off a current if it is too big; it is then reset
	compass	a magnet that is free to move so that its ends (poles) point to the north and south
	conduction (1)	electrical conduction - the flow of an electric current through a substance
	conduction (2)	thermal conduction - the transfer of heat (thermal energy) through a substance from hotter parts to colder parts
	conductors	substances that conduct heat or electricity
	constellations	patterns of stars in the sky
	convection	the transfer of heat (thermal energy) by the movement of a gas or liquid
	cooling towers	these are used in fuel powered power stations to change steam back into water after it has passed through the turbines
	copper	a metal that is a very good conductor of heat and electricity
	cosmic radiation	harmful radiation that comes from space
	critical angle	the angel at which you start to get total internal reflection
	cycle	one complete wave of an alternating current; the number of cycles per second is the frequency
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	D
	d.c.	short for direct current
	diodes	these let a current pass through them in only one direction
	direct current	d.c. for short; an electric current that always flows in the same direction
	drag	another word for air resistance
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	E
	earthed	something is earthed when it is connected to the ground with an electrical conductor
	echo	an echo occurs when sound or ultrasound is reflected straight back to where it came from
	efficiency	a measure of how much energy is usefully transferred as the form of energy you want
	elastic substance	something is elastic if it goes back to its original shape when you take away a force that was changing its shape
	elastic limit	if you change the shape of something beyond its elastic limit, it does not go back to its original shape
	elastic potential energy	the energy that is stored in an object such as a spring when a force changes its shape; sometimes called strain potential energy
	electric motor	this transfers electrical energy as kinetic (movement) energy
	electrodes	these are put into a melted or dissolved substance and connected to a battery or power supply so that electrolysis can happen
	electrolysis	the process of splitting up a melted or dissolved substance by passing an electric current through it
	electromagnet	a magnet that is only magnetised when an electric current is flowing through its coil
	electromagnetic radiation	radio waves, microwaves, infrared radiation, light, ultraviolet radiation, x-rays and gamma radiation are all types of electromagnetic radiation
	electromagnetic spectrum	the different types of electromagnetic radiation arranged in order of their wavelengths or frequencies
	electrons	tiny particles with a negative charge (-1); they move when you give a solid a charge of static electricity, or when a current flows through an electrical conductor
	ellipse	the squashed circle shape of the orbits of the planets around the Sun
	emit, emission	we say that radioactive substances emit radiation
	endoscope	this is used by doctors to see inside a patient's body
	extension	the change in the length of a spring or a wire when it is stretched by a force
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	F
	fluids	substances that can flow; liquids and gases are fluids
	fluorescent substances	substances that absorb ultraviolet radiation and transfer the energy as light
	fossil fuels	fuels that formed in the Earth's crust over millions of years from the remains of dead plants and animals, eg. coal, oil and natural gas; once used they cannot be replaced
	frequency	the number of complete waves or vibrations in a second; frequency is measured in units called hertz or cycles per second
	friction	a force which acts on an object that is moving; the force acts in the opposite direction to the direction in which the object is moving
	fuels	substances that release energy when they are burned; nuclear fuels release energy when their atoms are split in a nuclear reactor
	fuses	these protect an electrical circuit by melting if the current is too big; they then have to be replaced
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	G
	galaxies	groups of billions of stars
	gamma radiation	very short wavelength electromagnetic radiation; one of three types of radiation that radioactive substances can give out (emit)
	Geiger counter	this is used to measure the radiation from radioactive substances; a Geiger-Muller tube detects the radiation
	generator	this transfers kinetic (movement) energy as electricity
	geothermal energy	heat (thermal energy) from inside the Earth
	global warming	occurs when the extra carbon dioxide produced from burning fossil fuels adds to the greenhouse effect
	gravitational potential energy	the energy that is transferred to an object by lifting it against the force of gravity
	gravity	the force between objects because of their mass
	greenhouse effect	this describes the way in which the Earth is kept warm by gases such as carbon dioxide in the atmosphere; burning fossil fuels produces more carbon dioxide, so this adds to the green house effect - we call this global warming
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	H
	hertz	Hz for short; frequency is measured in units called hertz
	hydraulic systems	systems that use pressure in a fluid to send forces to where they are needed
	hydroelectricity	electricity generated using water collected behind a dam (which stores energy as gravitational potential energy)
	Hz	short for hertz
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	I
	induce, induction	the production of a voltage by moving a coil in a magnetic field, or by moving a magnet in a coil
	infrared	radiation that transfers heat (thermal energy) from hot objects; a form of electromagnetic radiation
	insulator (1)	electrical insulator - a substance that does not let electricity pass through it very easily
	insulator (2)	thermal insulator - a substance that does not conduct heat (thermal energy) very well
	ions	electrically charged particles in some melted or dissolved substances; ions move towards the electrodes during electrolysis
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	J
	J	short for joules
	joule	the unit of energy or work
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	K
	kilowatt-hours	kWh for short; 1 Unit of electricity; 1 kilowatt-hour is the energy transferred in 1 hour by a power of 1 kilowatt
	kilowatts	kW for short; 1 kilowatt is 1000 watts
	kinetic energy	this is the energy an object has because it is moving
	kW	short for kilowatt
	kWh	short for kilowatt-hour
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	L
	loudspeakers	these devices transfer electrical energy as sound
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	M
	magnetic field	the area around a magnet where it has an effect; lines of magnetic force show the shape of the magnetic field
	magnets	these attract iron and steel, and can attract or repel other magnets
	mains electricity	the electricity that is supplied to our homes
	mass	the amount of matter in an object; mass is measured in units called kilograms (kg)
	metals	substances that are good conductors of heat and electricity
	microwaves	electromagnetic radiation with a wavelength between that of radio waves and infrared radiation; they are used for cooking and to send signals to and from artificial satellites
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	N
	N	short for newtons
	National Grid	the network of cables that carry electricity from power stations to where it is used
	negative charge	the charge on an object that has gained electrons
	negative terminal	the side of a cell or power supply that electrons move away from
	neutrons	particles that may be found in the nucleus of an atom; a neutron has a mass of 1 unit but no electrical charge
	newtons	N for short; forces are measured in units called newtons
	nitrogen oxides	gases produced when fossil fuels burn; they are one of the causes of acid rain
	non-renewables	energy sources that gradually get used up and will eventually run out; they take many millions of years to be replaced
	normal	a line drawn at right angles to the boundary between two different substances
	nuclear fuels	radioactive substances such as uranium and plutonium which are used in nuclear power stations
	nucleus	the central part of an atom; the nucleus contains protons and neutrons
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	O
	orbit	the path of a planet around the Sun or a satellite around a planet; it can be a circle or an ellipse
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	P
	Pa	short for pascals
	parallel circuit	parts of a circuit are connected in parallel if an electric current can flow through each part separately
	pascals	Pa for short; pressure is measured in units called pascals - 1 Pa is the same as 1 newton per square metre
	permanent magnets	magnets that stay magnetised all the time
	photocopiers	these use static electrical charges to make copies of a printed page
	pitch	we hear sound with a high frequency as a note with a high pitch
	plane mirror	this is a flat mirror; light is reflected from the mirror at the same angle it strikes the mirror
	planets	very large objects, such as the Earth, which move in orbit around the Sun
	plutonium	a fuel used in nuclear power stations
	poles (1)	the parts of a magnet that attract or repel
	poles (2)	the parts of the Earth's surface that are on the axis round which it spins
	positive charge	the charge on an object that has lost electrons
	positive terminal	the side of a cell or power supply that electrons move towards
	potential difference	p.d. for short; another name for voltage
	power	how fast energy is transferred (or work is done); it is measured in units called watts or kilowatts
	pressure	this is the force on a certain area; pressure is measured in units called pascals
	protons	particles found in the nucleus of an atom; a proton has a mass of 1 unit and a positive charge of +1 unit
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	Q
	R
	radiation (1)	energy that travels as electromagnetic radiation, including heat (thermal energy), which is infrared radiation
	radiation (2)	what radioactive substances give out (emit)
	radiation dose	a measure of how much harmful radiation a person's body receives in a period of time
	radio waves	long wavelength electromagnetic radiation that we use to carry radio and television signals
	radioactive substances	substances that give out (emit) alpha, beta or gamma radiation
	reflection	reflection occurs when radiation (or a wave) bounces back from something it has hit
	refraction	refraction occurs when radiation (or a wave) changes direction when it crosses the boundary between two different substances; with water waves, this happens when water changes depth
	renewable	energy sources that are constantly being replaced and will not run out
	repel, repulsion	the force that pushes magnetised or electrically charged objects apart
	resistance	bulbs and other electrical components resist a current being pushed through them, so we say they have a resistance
	resistors	these can be used in an electrical circuit to increase the resistance and reduce the current
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	S
	satellites	objects that move in orbit around the Earth or another planet; the Moon is a satellite of the Earth; there are also artificial satellites
	series circuit	parts of a circuit are connected in series if the electric current flows through each part one after the other; there is no branching in this type of circuit
	solar cells	these transfer energy from the Sun's radiation directly as electricity
	solar panels	these absorb energy from the Sun's radiation and transfer it as heat (thermal energy)
	spectrum (1)	visible spectrum - this is what you get when you split white light into all the different colours from which it is made
	spectrum (2)	see electromagnetic spectrum
	speed	the distance something travels in a period of time
	start-up time	how long it takes to start up a power station and get it generating electricity
	static electricity	electrical charges that stand still; when charges move you get current electricity
	streamlined shape	a shape that produces very little friction when it moves through air or water
	sulphur dioxide	a gas that is produced when many fuels burn; it is one of the causes of acid rain
	symbols	a way of showing electrical components; they make it easy to draw circuit diagrams
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	T
	terminal velocity	the steady speed reached by a falling object when its weight is exactly balanced by friction or air resistance
	total internal reflection	when all of a beam of light inside glass (or another transparent substance) is reflected from the inside boundary between the glass and the air
	transformers	these are used to increase (step-up transformers) or to reduce (step-down transformers) the voltage of an a.c. supply which is fed into them
	transmit, transmission	this occurs when a substance allows waves or radiation to pass through it
	turbine	this is made to turn by moving water, steam or wind; it transfers kinetic (movement) energy as its own kinetic energy; it can be used to turn a generator
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	U
	ultrasonics, ultrasound	sound waves which have a frequency that is too high to hear (above 20,000Hz)
	ultraviolet radiation	electromagnetic radiation with a wavelength shorter than that of violet light waves
	Units	we buy mains electricity in Units; 1 Unit is the same as 1 kilowatt-hour
	Universe	everything there is; it is made up of billions of galaxies
	uranium	a fuel used in nuclear power stations
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	V
	V	short for volts
	vacuum	empty space
	vacuum flask	a container that has a vacuum between two walls to reduce heat transfer
	velocity	this is the speed of an object and its direction
	voltage	the 'push' of an electrical supply
	voltmeter	this is used to measure voltage
	volts	V for short; the 'push' of an electrical supply is measured in units called volts
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	W
	W	short for watts
	watts	power is measured in units called watts; 1 watt is 1 joule of energy transferred per second
	wavelength	the distance between one point on a wave and the same point on the next wave
	waves	evenly spaced out disturbances that carry energy from one place to another
	weight	the force of gravity on an objects; it is measured in units called newtons
	wind farm	a lot of wind generators in the same place
	work	the energy transferred when a force is moved through a distance; work is measured in units called joules
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	X
	x-rays	short wavelength electromagnetic radiation; they can pass though flesh but is stopped by bone and metal
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	Y
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	Z