2 Electricity
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Electricity units
2.1
Use the following units: ampere (A), coulomb (C), joule (J), ohm (Ω), second (s), volt (V) and watt (W)
(b) Mains electricity
2.2Electrical safety devices
Understand how the use of insulation, double insulation, earthing, fuses and circuit breakers protects the device or user in a range of domestic appliances
2.3Heating effect of current
Understand why a current in a resistor results in the electrical transfer of energy and an increase in temperature, and how this can be used in a variety of domestic contexts
2.4Power, current and voltage
Know and use power = current × voltage, P = IV, and apply it to selecting appropriate fuses.
2.5Electrical energy transfer
Use energy transferred = current × voltage × time, E = IVt.
2.6AC and DC
Know the difference between mains electricity being alternating current (a.c.) and direct current (d.c.) being supplied by a cell or battery
(c) Energy and voltage in circuits
2.7Series and parallel circuits
Explain why a series or parallel circuit is more appropriate for particular applications, including domestic lighting
2.8Current in series circuits
Understand how the current in a series circuit depends on the applied voltage and the number and nature of other components
2.9Current-voltage practical
Describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how to investigate this experimentally
2.10Resistance and current
Describe the qualitative effect of changing resistance on the current in a circuit
2.11LDRs and thermistors
Describe the qualitative variation of resistance of light-dependent resistors (LDRs) with illumination and thermistors with temperature
2.12Lamps and LEDs
Know that lamps and LEDs can be used to indicate the presence of a current in a circuit
2.13Voltage, current and resistance
Know and use voltage = current × resistance, V = IR.
2.14Current as charge flow
Know that current is the rate of flow of charge
2.15Charge, current and time
Know and use charge = current × time, Q = It.
2.16Electron flow in metals
Know that electric current in solid metallic conductors is a flow of negatively charged electrons
2.17Current at junctions
Understand why current is conserved at a junction in a circuit
2.18Parallel voltage
Know that the voltage across two components connected in parallel is the same
2.19Series circuit calculations
Calculate the currents, voltages and resistances of two resistive components connected in a series circuit
2.20Voltage and energy per charge
Know that: • voltage is the energy transferred per unit charge passed • the volt is a joule per coulomb
2.21Energy, charge and voltage
Know and use energy transferred = charge × voltage, E = QV.
(d) Electric charge
2.22PConductors and insulators
Identify common materials that are electrical conductors or insulators, including metals and plastics
2.23PCharging by friction practical
Practical: investigate how insulating materials can be charged by friction
2.24PProducing electrostatic charge
Explain how positive and negative electrostatic charges are produced on materials by the loss and gain of electrons
2.25PAttraction and repulsion
Know that there are forces of attraction between unlike charges and forces of repulsion between like charges
2.26PElectrostatic phenomena
Explain electrostatic phenomena in terms of the movement of electrons
2.27PElectrostatic dangers
Explain the potential dangers of electrostatic charges, e.g. when fuelling aircraft and tankers
2.28PElectrostatic uses
Explain some uses of electrostatic charges, e.g. in photocopiers and inkjet printers