GCSE Physics · Edexcel 1PH0 · Topic 10A
Current, potential difference and resistance
Key points
- Current () is the rate of flow of charge: , in amperes (A). An ammeter is connected in series.
- Potential difference () is the energy transferred per unit charge: , in volts (V). A voltmeter is connected in parallel.
- Resistance: , in ohms (Ω).
- I–V graphs: a fixed resistor gives a straight line through the origin; a filament lamp curves because resistance rises as it heats; a diode only lets current flow one way.
- An LDR's resistance falls as light intensity increases; a thermistor's resistance falls as temperature increases.
- In metals, current is a flow of electrons; collisions with ions cause heating and resistance.
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Current, potential difference and resistance are the three quantities you need for every circuit calculation. This sub-topic defines them, links them, and shows how different components respond when the potential difference across them…
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