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LearnEdexcel4PH12017 specificationPaper 2P · Paper 2 (all content)Electricity

Paper 2P · Module

Electricity

4 subtopics≈ 125 min in total

Start the module: Charge, current and potential difference Open graphing calculator

Charge, current and potential difference
Electric current is the rate of flow of charge, $I=\dfrac Qt$ , measured with an ammeter in series. Potential difference (and e.m.f.) is the energy transferred per unit charge, $V=\dfrac WQ$ , measured with a voltmeter in parallel. Rubbing insulators transfers electrons, giving them static charge; like charges repel and unlike charges attract.
≈ 30 min
Resistance
Resistance tells you how hard it is for current to flow: $R=\dfrac VI$ , in ohms (Ω). A fixed resistor at constant temperature has a straight-line $I$ – $V$ graph; a filament lamp curves because its resistance rises as it heats; a diode lets current through in one direction only. Longer, thinner wires have more resistance.
≈ 30 min
Series and parallel circuits
In series, the current is the same everywhere, p.d.s add up to the supply, and resistances add. In parallel, each branch gets the full p.d., the branch currents add up to the total, and the combined resistance is less than any single branch. A potential divider shares the supply p.d. in the ratio of its resistances.
≈ 35 min
Electrical power, energy and safety
Electrical power is $P=IV$ , and the energy transferred is $E=IVt$ . Electricity companies charge per kilowatt-hour: the energy used by a $1$ kW appliance in $1$ hour. Fuses and circuit breakers cut off the current if it gets too big; earthing a metal case makes a fault blow the fuse instead of electrocuting you.
≈ 30 min