GCSE Physics, Unit 2, Lesson 2 of 6

Potential difference and resistance

GCSE Physics, Electric circuits, 20 minutes

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What potential difference and resistance are, V = IR in every arrangement, and working in kΩ and mA.

What you will learn

  • Explain what potential difference and resistance are
  • Calculate V, I or R with V = IR
  • Convert kΩ to Ω and mA to A inside a calculation

Potential difference

The potential difference (p.d.) across a component is the push that drives charge through it.

It tells you how much energy each coulomb of charge transfers: 1 volt is 1 joule per coulomb. So potential difference is the energy transferred per unit charge between two points in a circuit, measured in volts (V). Many people call it the voltage.

You measure it with a voltmeter connected across the component, in parallel:

AV3 Vlamp

Here the ammeter is in series with the lamp and the voltmeter is across the lamp. The bigger the p.d. across a component, the bigger the current through it.

The rest of this lesson and its 7 practice questions are locked.

In this lesson

  1. Potential difference
  2. Resistance and V = IR
  3. kΩ and mA
  4. Measuring an unknown resistance
  5. Try it: Check V = IR with the calculator
  6. Try it: Your first V = IR question

7 practice questions, marked as you go; about 20 minutes in all.

Key terms

Potential difference, Voltage, Across, Resistance, Directly proportional, Inversely proportional, Rheostat

In this unit: Electric circuits

Circuit symbols, charge and current, V = IR, I-V graphs, series and parallel circuits, and sensing circuits with LDRs and thermistors.

All of Electric circuits

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