Electricity

current

the rate of flow of electric charge

LDR

type of resistor which is affected by changes in light levels

diode

An electrical device that allows current to flow in one direction only

thermistor

An electrical device whose resistance decreases as its temperature increases.

fixed resistor

Electrical component with a resistance that is fixed and cannot be changed.

variable resistor

A resistor where the value of the resistance can be changed.

What is the equation for charge?

charge = current × time

Q = I x t

resistance

The opposition in an electrical component to the movement of electrical charge through it.

potential difference

The potential difference (or voltage) of a supply is a measure of the energy given to the charge carriers in a circuit. Units = volts (V)

Equation for potential difference

V = E/Q

direct current

An electric current that flows in one direction only

alternating current

An electric current that regularly changes its direction and size

step up transformer

A transformer that increases the voltage of the ac supply.

step down transformer

A transformer that decreases the voltage of the ac supply

filament bulb

• Thin piece of wire

• Metal ions

• Collision between electrons and metal ions increase as voltage and therefore temperature increases

ohmic conductor

Voltage and current are directly proportional

ohms law

the current flowing through a wire is proportional to the voltage across provided the temperature remains constant