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identify cells, batteries and generators as electrical sources, and bulbs, resistors, bells, motors, LEDs, LDRs, thermistors and buzzers as parts of an electrical circuit where electrical energy is dissipated. [The electrical symbols for a cell, battery, power supply, filament bulb, switch, LDR, fixed and variable resistor, LED, motor, heater, thermistor, ammeter and voltmeter should be known.]

recall that resistors are heated when electric current passes through them.

describe and explain the effect of a variable resistor in controlling the brightness of a lamp and the speed of a motor.

measure resistance by correctly placing a voltmeter and an ammeter in a circuit.

state and be able to use the equation V= I R Voltage or potential difference (volts) = Current (Amps) x Resistance (Ohms)

describe how current varies with voltage in a metal wire at constant temperature, a filament bulb and a silicon diode. N.

describe how the resistance of an LDR varies with light level.

describe how the resistance of a thermistor (ntc only) varies with temperature. .

state and be able to use the equation charge = current x time. charge (coulombs) = current (amps) x time (seconds)

explain that the current in a metal is due to a flow of electrons from negative to positive and explain that a current in an electrolytic solution is due to a flow of both positively and negatively charged particles.

recall that the voltage between two points is the number of joules of energy transferred for each coulomb of charge that passes between the points.

Electricity in the Home

state and be able to use the equation power = voltage x current. watts = amps x volts

explain that a direct current is always in the same direction but an alternating current changes direction.

recall that energy is supplied to houses via the live and neutral wires.

recall that in normal use no current passes in the earth wire.

explain that the live wire has to be insulated from the earth and neutral wires.

explain how fuses and circuit breakers prevent fire due to electrical faults.

explain how the earth wire, together with the fuse or circuit breaker, prevents electrocution.

explain why double-insulated appliances do not need an earth wire.

explain that energy can be transferred from the electricity supply by means of convection currents and also as electromagnetic waves, including infra-red and microwaves.

use the equation energy = power x time to calculate energy transfer in joules and kilowatt-hours. kilowatt hours (units) = kilowatts x hours

recall that a domestic electricity meter measures the energy transfer in kilowatt- hours.

calculate the cost of electrical energy from a knowledge of the power, the time and the unit cost.

Candidates should be able to :

Electrostatic Phenomena

explain that when two objects rub together and become charged, electrons are transferred from one object to the other.

explain how charging by contact and charging by induction occur in terms of the movement of electrons.

recall that there are repulsive forces between objects with similar charges, and attractive forces between objects with opposite charges.

Uses of Electrostatics

describe some everyday beneficial uses of electrostatic charge and examples of where the build-up of static charge should be avoided, to include photocopying, ink-jet printers, the removal of ash from the waste gases in a coal-burning power station and refuelling of aircraft.

Electrostatics and Current

recall that current is a flow of charge.

state and be able to use the equation charge = current x time. charge (coulombs) = current (amps) x time (seconds)

recall that the voltage between two points is the number of joules of energy transferred for each coulomb of charge that passes between the points.