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Electricity

Ammeter=

measures the current (flow of electrons in a circuit)

Batteries

provide a push the electrons to flow around the circuit, the cell gives

potential difference (v) - makes the circuit go. This is measured in volts with

a voltmeter.

The

bulb converts electrical energy to light energy.

Symbols:

·

A diode allows current through in one direction only

·

LED (Light emitting diode) emits when a current passes

through it.

·

A fixed resistor limits current in a circuit

·

A variable resistor allows the current to be varied

·

A fuse is designed to melt and ‘break’ the circuit of the

current in the circuit is greater than a certain amount.

Circuits

Current is the ‘flow’ of electrons around a circuit. We

measure current with an ammeter and the units are called ‘amps’. We put our

ammeter in series with the thing we’re measuring.

Voltage is like a ‘push’ from a battery that makes a

current flow. It’s also called ‘potential difference’ or ‘p.d.’

We measure voltage with a voltmeter. The units are called

‘volts’, we put our voltmeter in a parallel circuit with the thing we are

measuring.

In circuit the cell

provides energy. This is passed around the circuit by the current. As the

current flows through a component, electrical energy is transformed in

different form. I.e. light and heat.

The more cells that are in circuit the greater the voltage will be. The greater

the voltage the more energy that will be transformed by the bulbs and so

brighter they will be.

In a series and parallel circuit

the voltage will be different. Parallel circuits’ voltage is the same because a

voltmeter would show the same reading as electron from a cell would either pass

through one component or the other. Meaning it would deliver the same amount of

energy.

Series circuit= same current all-around circuit, voltage is shared

between the bulbs

A1= A2

Parallel circuit= current changes, voltage is the same

A1=A2+A3

Ohms law states that

the current flowing through a conductor is proportional to the voltage across

it. Therefore,

V=IR

V= Voltage

I= current

R= Resistance

Resistance is about how

many electrons can flow in a circuit. The more electrons that can flow, the

lower the resistance. The fewer electrons that can flow, the higher the

resistance. ‘High resistance’

electrons find it harder for electrons to flow.

‘Low resistance’ electrons

find it easy to flow through the circuits.

Resistors,

filament lamps and diodes produce different current-potential difference

graphs. The resistance of thermistors depends on the temperature, while the

resistance of light-dependent resistors (LDRs) depends on the light intensity =

IMPORTANT (learn graphs for each one)

Static electricity

Like charges repel from

each other

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