physics paper 2

energy

Something that is needed to make things happen or change.

power

The amount (rate) of energy transferred per second. The units are watts (W).

watt

The unit for measuring power. Equal to 1 joule of energy transferred every second.

work done

A measure of the energy transferred when a force acts through a distance.

action−reaction forces

Pairs of forces on interacting objects. They are always the same size, in opposite directions, and acting on different objects. They are not the same as balanced forces, which act on a single object.

contact forces

Forces for which objects need to touch before the force can have an effect (e.g. friction or upthrust).

electric field

The space around an object with a charge of static electricity, where it can affect other objects. The first word is sometimes replaced with "electrostatic".

force field

The space around something where a non-contact force affects things. Examples include magnetic fields and gravitational fields.

friction

A force between two surfaces that resists motion.

gravitational field

The space around any object with mass where its gravity attracts other masses.

magnet

An object that has its own magnetic field around it.

magnetic field

The area around a magnet where it can affect magnetic materials.

magnetic material

A material such as iron that is attracted to a magnet.

magnetism

The force caused by magnets or magnetic materials.

magnitude

The size of something, such as the size of a force or the measurement of a distance.

non-contact force

A force that can affect something from a distance (e.g. gravity).

normal contact force

A force that acts at right angles to a surface as a reaction to a force on that surface.

scalar quantity

A quantity that has a magnitude (size) but not a direction. Examples include mass, distance, energy and speed.

static electricity

Electric charges on insulating materials.

upthrust

A force that pushes things up in liquids and gases.

vector

A quantity that has both size and direction.

component

One of two forces at right angles to each other, resolved from a single force.

free body force diagram

A diagram of an object showing all the forces acting on it and the size and direction of those forces.

net force

Another term for resultant force.

resolving

Representing a single force as two forces at right angles to each other.

resultant force

The total force that results from two or more forces acting upon a single object. It is found by adding together the forces, taking into account their directions. Another term for net force.

scale diagram

A way of working out the resultant forces or component forces by drawing a diagram where the lengths of arrows represent the sizes of the forces.

vector diagram

A diagram on which vectors are displayed (e.g. a scale diagram, a free body force diagram).

gears

A system of toothed wheels. The teeth interlock so that turning one wheel turns the one in contact with it. If different sizes are used, the speed of rotation or the force transmitted can be changed.

equilibrium

When things are balanced and not changing they are said to be in this.

lever

A simple machine that consists of a long bar and a pivot. It can increase the size of a force or increase the distance the force moves.

moment

The turning effect of a force. It is calculated by multiplying the force by the distance between the force and the pivot, measured at right angles to the force (this is called the normal distance).

newton metre

The unit for the moment of a force. Symbol Nm.

normal

At right angles to.

atom

The smallest neutral part of an element that can take part in chemical reactions.

battery

More than one cell joined together.

component

A part of something e.g. a lamp might be a component of an electrical circuit.

electron

A tiny particle with a negative charge and negligible mass.

neutron

A particle found in the nucleus of an atom, having zero charge and a mass of 1 (relative to a proton).

nucleus

The central part of an atom.

parallel circuit

A circuit in which there is more than one path for the current to follow.

proton

A particle found in the nucleus of an atom, having a positive charge and the same mass as a neutron.

series circuit

A type of circuit with only one loop of wire.

shell

A distinct region around a nucleus that can be occupied by electrons and is usually drawn as a circle. Sometimes called an orbit.

voltage

The energy transferred to or from a coulomb of electric charge when it flows between two points.

ampere

The unit for current. Can be shortened to amp. Symbol A.

ammeter

A meter used to measure current.

cell

A chemical store of energy that can be transferred by electricity.

conserved

Kept the same throughout.

potential difference

The energy transferred to or from a coulomb of electric charge when it flows between two points. Sometimes called voltage or shortened to pd.

voltmeter

Meter used to measure potential difference (or voltage).

volt

The unit for potential difference (or voltage).

charge

A basic property of matter that causes forces between charged particles or objects. It can be positive or negative.

coulomb

The unit for measuring charge.

rate

How quickly something happens.

ohm

The unit for measuring electrical resistance. (Ω)

resistance

A measurement of how difficult it is for electricity to flow through something.

directly proportional

A relationship in which when one variable is multiplied by any number the other variable is multiplied by the same number, e.g. doubling one variable doubles the other. Seen as a straight line through the origin when the two variables are plotted on a scatter graph.

diode

A component that lets electric current flow through it in one direction only.

light-dependent resistor

A resistor whose resistance gets lower when light shines on it. Abbreviated to LDR.

thermistor

A component whose resistance changes as its temperature changes. In GCSE they all increase in resistance as the temperature increases.

dissipated

Spread out.

work

Done when a force moves an object through a distance, e.g. when a charged particle is moved between two points in an electric field. The unit is the joule (J).

power

The amount (rate) of energy transferred per second. The units are watts (W).

power rating

The energy transferred per second by an appliance.

watt

The unit for measuring power. Equal to 1 joule of energy transferred every second.

alternating current

Current whose direction changes many times each second. Abbreviated to AC.

direct current

A current that flows in one direction only, such as the current produced by a battery. Abbreviated to DC.

hertz

The unit for frequency, equal to one wave per second.

mains electricity

Electricity supplied from power stations using the national grid.

national grid

The system of wires and transformers that distributes electricity around the country.

thermal energy store

The hotter something is, the more energy it has in this. It is sometimes called 'heat'.

circuit breaker

An electrical component that switches off the current in a circuit if there is a fault and the current rises to dangerous levels. It can be switched back on when the fault is fixed.

earth wire

A low-resistance path for electric current to flow to earth for safety if there is a fault in an appliance.

fuse

A safety device containing a length of wire that is designed to melt if the current in a circuit gets too hot.

live wire

The wire connected to the a.c. supply from the power station. The voltage oscillates between the maximum V in one direction and the maximum V in the opposite direction.

neutral wire

A neutral wire is held at or near earth potential (0 V). It completes the circuit to the power station and carries current.

charge

A conserved property of some particles (e.g. electron, proton) which causes them to exert forces on each other. An electron has a negative value, and a proton has a positive value.

induction

The creation of something in something else by the action of an external influence. For example, a negatively charged object can induce a positive charge on a neutral object that is brought near it.

insulator

A barrier to the transfer of something (usually energy). An electrical one of these does not conduct electricity, and will not allow electrons to flow freely through it.

static electricity

Unbalanced electric charges on the surface or within a material.

discharge

To remove an electric charge by conduction.

earthing

When something is connected to the Earth by a conductor so that electric charges can flow between it and the Earth.

electrostatic spraying

When the droplets of a substance being sprayed are given an electric charge.

electric field

The space around an electrically charged object where it can affect other objects. The first word is sometimes replaced with "electrostatic".

field lines

Lines that show where forces are stronger or weaker, and show the direction of a field.

force field

The space around something where a non-contact force affects things. Examples include magnetic fields, gravitational fields and electric fields.

point charge

A charge with a very small volume; a uniform sphere whose charge acts as if it is concentrated at the centre.

uniform

The same in all places.

core

The innermost part of something e.g. the central part of the Earth.

induced magnet

A piece of material that becomes a magnet because it is in the magnetic field of another magnet.

magnetic field

The area around a magnet where it can affect magnetic materials or induce a current.

magnetic material

A material, such as iron, that is attracted to a magnet.

permanent magnet

A magnet that is always magnetic, such as a bar magnet.

plotting compass

A small device with a needle, used to find the shape of a magnetic field.

electromagnet

A magnet made using a coil of wire with electricity flowing through it. Also called a solenoid.

solenoid

A coil of wire with electricity flowing in it. Also called an electromagnet.

temporary magnet

A magnet that is not always magnetic, such as an electromagnet or an induced magnet.

carbon brush

A block of carbon that makes electrical contact between a circuit and a moving object such as a slip ring or commutator.

Fleming's left hand rule

A way of remembering the direction of the force when a current flows in a magnetic field. The thumb shows the direction of the force, the first finger shows the direction of the magnetic field (N to S) and the second finger shows the current (+ to −).