Potential difference, the volt, the ohm and Ohm's law
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Why batteries have volts
- Potential difference
Read the transcript of the teaching part
Last time
Before we start: last time, in Resistivity, drift speed and charge carriers, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Why batteries have volts
Two batteries, both put into the same torch. One lights the bulb brightly, the other dimly. The brighter one gives more energy to each coulomb of charge that passes through. That energy per charge is the potential difference, measured in volts.
Potential difference
The potential difference across a component is the energy transferred, from electrical energy to other forms, per unit charge passing through it. As an equation, V equals W over Q. Rearranged, W equals Q V. It is not energy per unit current, and not power per unit charge. Power over current gives the value of p.d., but is not its definition. Six volts across a component, with three coulombs passing, transfers eighteen joules.
Chapter 9.2: Potential difference and resistance
- Potential difference, the volt, the ohm and Ohm's law 5 min
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