National 5 Physics - Electricity

(Electric) Current

the electric charge transferred per unit of time.

I = Q/t

Alternating current

a current in which the direction of the flow of charge continuously changes

Direct current

a current in which the direction of the flow of charge does not change

Oscilloscope

a device which allows the observation of varying voltage signals over time, typically used to study alternating currents and waves.

Electric field

region of space around a charged object in which another charge will experience a force.

Point charge

a charge which occupies a single point in space with zero volume.

Uniform field

an electric field which does not change strength or direction

Potential difference (voltage)

the energy per unit of charge

Ohm's Law

the voltage across a component is directly proportional to the current through it.

Potential divider

a circuit consisting of two resistors in series which split the potential difference between them in proportion to their resistance.

Series circuit

a circuit with only one path the current can follow around it.

Parallel circuit

a circuit with more than one path the current can follow around it.

Cell

converts chemical energy to electrical energy

Battery

converts chemical energy to electrical energy, made of more than one cell joined together

Lamp

converts electrical energy to light (and heat)

Switch

used to turn a circuit on or off

Resistor

used to control the size of current and voltage for other component, converts electrical energy into heat

Voltmeter

used to measure the potential difference across a component, needs to be connected in parallel

Ammeter

used to measure the current through a component, needs to be connected in series

Ohmmeter

used the measure the resistance of a component, needs to be used without a power supply

LED

semiconductor device that converts electrical energy to light, much more efficient than a lamp

Motor

converts electrical energy to kinetic (and heat), spins

Microphone

converts sound energy into electrical energy

Loudspeaker

converts electrical energy into sound energy (and heat)

Photovoltaic cell

converts light energy into electrical energy

Fuse

safety device that breaks the circuit if the current through it gets too high

Diode

device that allows current to flow through it in one direction only.

Capacitor

device that stores electrical charge and energy

Thermistor

a variable resistor whose resistance increases when the temperature decreases

LDR

light dependent resistor, a variable resistor whose resistance increases when the light level decreases

Relay

an automatic electromagnetic switch, used to safely switch on a high voltage/high current circuit using a low voltage and current

(NPN) Transistor

an electronic switch, switches on automatically if the voltage increases above a set value

MOSFET

an electronic switch, switches on automatically if the voltage increases above a set value

Switching circuit

a circuit that combines a potential divider and transistor to switch on output device on and off automatically.

(Electrical) power

(electrical) energy transferred per unit of time

Fuse rating

the maximum current that can flow through a fuse before it will blow and cut the current.