Electricity

Electricity

• Static• Is stationaryE.g. Brush your

hairWool socks

in tumble drier

• Current• Flows around

circuitE.g. turn on light

Walkman

Electricity occurs in 2 different forms

Static Electricity

• Occurs with materials which are insulators

• Rubbing adds or removes electrons

• Object becomes charged• Like objects repel, unlike attract

Current Electricity

• Electrons flow through a conductor• Negative to positive• Circuit = continuous loop for

electrons to flow• Needs energy supply• Energy user

Electrical components

• Wire• Ammeter• Battery• Fuse• Connected wires

• Bulb• Switch• Voltmeter• diode• Resistor• Rheostat

CIRCUIT TYPESThe simplest type of circuit involves electricity going around with no “choices” (electrons don’t really choose).

This is called a Series circuit.

Draw the path the electrons travel.

The other main type of circuit has two or more branches.

This is called a Parallel circuit.

Draw on the electron flow.

What sort of circuit is this?

A parallel… but, more importantly…

A short circuit.

Series circuit

• Has a single loop for electrons to travel round

• Components are connected one after another

• Current has to travel through all components

• Current is the same at all points• Voltage is shared between

components

Parallel circuit

• Has two or more paths for electrons to flow down

• Current is shared between the branches

• Sum of the current in each branch = total current

• Voltage loss is the same across all components

Current (I)

Current is the flow of electronsaround a circuit• DC = direct current like battery• Electrons flow in one direction• AC = Alternating current like mains• Electron flow changes direction

50x per second

Ammeter

• Measures CURRENT(I)• Unit = Amp (A)• Current is flow of electrons• Connect in series at the point you

wish to measure• RED to RED and BLACK to BLACK

3 pin plug

• 3 wires• P = phase (brown or red)• N = neutral (blue or black)• E = earth (yellow/green or green)

Voltage (V)

Gain or loss of energy as itpasses through a component• Voltage lost = voltage gained• In series voltage loss is shared

between components• In parallel voltage loss is the same

across all components

Voltmeter

• Measures voltage• Unit = Volt (V)• Voltage increases as it passes

through energy suppliers• Voltage is decreased as it passes

through users• Connect in parallel around a

component

SUMMARY

In Series In Parallel

Current

Voltage

Always the same The branches share electrons and add to the total

Voltage from source = voltage used

Voltage is shared between power users

Voltage is the same in all branches

Electricity Generation

Fossil Fuels

Hydro Dam

Hydroelectric power

Nuclear power

Wind Power

Tidal Power

Geothermal

Solar

• Solar water heating• Photovoltaic cells• Solar furnace

Resistance (R)

The amount that a component slows the current

• As the electrons are slowed by a resistor, energy is lost in the form of heat.

• This means that current, resistance and voltage must be linked.

• This is Ohms law

• The unit of resistance is the ohm, symbol V

I R×

Power

Energy used by component per second

• Unit of power is the Watt, symbol is W• One watt means that 1 joule of electrical

energy is being used up per second.• Current, voltage and power

are linked P

I V×

PROBLEMS

1. Fill in the gaps in the table.

a b

c d

e f

g h

i j

k l