GCSE Physics · AQA 8463 · Topic 4.2
Electricity
Key points
- Current is the rate of flow of charge: . Potential difference is the energy transferred per unit charge: .
- Resistance links them: . Ohmic conductors at constant temperature have constant resistance; filament lamps, diodes, thermistors and LDRs do not.
- In series circuits current is the same everywhere and p.d.s add up; in parallel circuits p.d. is the same across each branch and currents add up.
- UK mains is alternating current at 50 Hz and about 230 V. Plugs have live (brown), neutral (blue) and earth (green and yellow) wires.
- Power and energy: , , and . The National Grid uses step-up and step-down transformers.
- Static electricity (separate physics): rubbing insulators transfers electrons; charged objects create electric fields that exert forces on other charges.
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Electricity is about charge flowing round circuits and the energy it carries. This topic builds from the basic quantities (charge, current, potential difference and resistance) to real circuits, the mains supply in your home and the charges…
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