Module 5: Energy and electricity

Module 5: Energy and electricity

Units
Candidates will be assessed on their ability to:

use the following units:

� volt (V), ampere (A), ohm (..), watt (W), kilowatt-hour (kWh) (5.01)

Circuits
Candidates will be assessed on their ability to:

recall that cells and batteries supply direct current and understand that direct current (d.c.) passes in one direction only (5.02)

explain how changing the resistance in a circuit changes the current and how this can be achieved using a variable resistor (5.03)

describe how a voltmeter is placed in parallel with a component to measure the voltage (in volts) across it (5.04)

understand how the current in a series circuit depends on the voltage of the source (5.05)

recall and use the equation

� voltage (V) = current (A) � resistance (..)

� V = I � R (5.06)

describe how current varies with voltage for the following devices

� fixed value resistors

� filament lamps

� diodes

and how this can be investigated experimentally (5.07)

describe how the resistance of a light-dependent resistor (LDR) changes with light intensity and the resistance of a thermistor changes with a change of temperature (5.08)

Mains electricity
Candidates will be assessed on their ability to:

recall that the mains supply is alternating current and understand that alternating current (a.c.) changes direction (5.09)

recall that the mains supply can provide dangerous currents which can cause serious injury, or death, to users (5.10)

recall the functions of live, neutral and earth wires

� energy flows into a building or appliance through the live wire

� the neutral wire is needed to make a complete circuit

the earth wire, together with the fuse, prevents electrocution (5.11)

identify the live, neutral and earth conductors in a correctly wired plug and recall the colour of the insulation used on each conductor (5.12)

recall that a fuse is placed in the live conductor and understand that the fuse protects the appliance, circuit and connecting wires from overheating (5.13)

understand the action of a fuse

� a large current heats and melts a length of wire

� the melting of the wire breaks the circuit

� the correct choice of fuse depends on the current rating of an appliance (5.14)

understand that a residual current circuit breaker (RCCB)

� detects any difference in the currents in the live and neutral conductors

� acts quickly to protect the user should a leak to earth occur

� can be easily reset (5.15)

explain the use of insulation and double insulation in terms of safety, eg hairdryer, drill, vacuum cleaner (5.16)

understand that when an electric current passes through a resistor there is an energy transfer and the resistor is heated (5.17)

describe how the heating effect of an electric current is used in a variety of appliances, such as

� electric bar heaters

� immersion heaters

� kettles, cookers and irons (5.18)

understand that energy from the mains supply is measured in kilowatt-hours (5.19)

use the equation given below for calculating the cost of electricity

� cost = power (kW) � time (h) � cost of 1 kWh

(This equation will be provided if required) (5.20)

Energy resources and transfer
Candidates will be assessed on their ability to:

explain that an electric current is generated by a magnet rotating inside a coil of wire

� on a small scale, as in a bicycle dynamo

� in the large-scale generation of electrical energy (5.21)

recall how transformers are used in the transmission of electricity in the National Grid and explain the advantages and disadvantages of using overhead and underground cables (5.22)

understand a range of energy transfer chains illustrating the environmental implications of generating electricity

� the use of wind and water in electricity generation

� fossil fuel reserves and their use in electricity

� solar heating systems and electricity production through solar cells (5.23)

describe the advantages and disadvantages of methods of large scale electricity production using a variety of renewable and non-renewable resources (5.24)

understand the benefits of the use of low energy appliances, e.g. low energy light bulbs (5.25)

understand that insulation can reduce the transfer of energy between objects at different temperatures (5.26)

describe some examples where the use of insulation results in the reduction of energy transfer:

� loft insulation

� double glazing

� cavity wall insulation (5.27)

understand that many insulating materials make use of the insulating properties of air that is not free to form convection currents (5.28)