# P5

P5 module

- Created by: Laura Godfrey
- Created on: 01-04-10 11:14

## Static electricity

Static electricity is created when two objects are rubbed together

objects recieving electons = negatively charged

objects giving up electrons = positively charged

two materials with same charges = repel each other

two materials with different charges = attract each other

## Static electricity

Static electricity is created when two objects are rubbed together

objects recieving electons = negatively charged

objects giving up electrons = positively charged

two materials with same charges = repel each other

two materials with different charges = attract each other

## Current and Potential difference

Current = flow of charge measured in amperes

Direct current = flows in same direction

Alternating current = constantly changes direction

Metal conductors = lots of charges are free to move

Insulators = no charges free to move

Potential difference = voltage = measured in volts

Adding batteries in series = increases voltage and current

Adding batteries in parallell = potential difference and current stays same and each battry supplies less current

## Current and Potential difference

Current = flow of charge measured in amperes

Direct current = flows in same direction

Alternating current = constantly changes direction

Metal conductors = lots of charges are free to move

Insulators = no charges free to move

Potential difference = voltage = measured in volts

Adding batteries in series = increases voltage and current

Adding batteries in parallell = potential difference and current stays same and each battry supplies less current

## Resistance

Components = resist flow of charge

Electric current flows through component = component heats up

Greater resistance in a circuit = smaller current

Adding resistors in series = increases total resistance

Adding resistors in parallel = reduces total resistance and increases current through battery.

Current- potential difference graphs = current through resistor is directly proportional to voltage across resistor

Thermistor = resistance depends on temperature

LDR = resistance depends on light intensity

## Resistance

Components = resist flow of charge

Electric current flows through component = component heats up

Greater resistance in a circuit = smaller current

Adding resistors in series = increases total resistance

Adding resistors in parallel = reduces total resistance and increases current through battery.

Current- potential difference graphs = current through resistor is directly proportional to voltage across resistor

Thermistor = resistance depends on temperature

LDR = resistance depends on light intensity

## Circuits

In series circuits....

- current flowing through each component is the same

- potential difference across components add up to that across the battery

- potential difference is largest across components with greatest resistance

In parallel circuits...

- current flowing through each component depends on resistance

- current running to and from battery is equal to sum of current through each parallel component

- current is smallest across components with greatest resistance

## Electromagnetic Induction

When a magnet is moved into a coil of wire, a voltage is induced. If ends of coil are connected a current is induced.

Current can be induced in opposite direction by...

- moving magnet out of coil

- moving other pole of magnet into coil

Electric generators = use electromagnetic induction. produce mains electricity

Generators produce alternating current as the direction of flow is reversed every half turn of the magnet

Transformers = used to change the voltage of an alternating current

## Power and energy

Power = measure of the rate of energy transfer

Power (W) = potential difference (V) x current (A)

Energy = measured in joules. Domestic energy is measured in kilowatt hours as joules are very small amounts of energy

Energy transferred (J) (kWh) = Power (W) (kW) x Time (S) (h)

Efficiency = the proportion of energy that is usefully transferred by an applliance

Efficiency (%) = energy usefully transferred / total energy supplied x 100

## Comments