IGCSE · Cambridge (CIE) · 0972

Current, voltage and resistance

Connect the movement of charge with the energy supplied by a circuit.

What you will learn

Explain current and potential difference.
Use V=IR with consistent units.

Different quantities describe a circuit

Current is the rate at which charge passes a point. Potential difference is energy transferred per unit charge between two points. Resistance describes the ratio of potential difference across a component to the current through it.

An ammeter measures current in series. A voltmeter measures potential difference in parallel across the component. These arrangements reflect what each instrument is measuring.

Calculate and interpret resistance

Rearrange V=IR to isolate the required quantity before substituting. For an ohmic conductor at constant temperature, V is proportional to I and resistance remains constant. A filament lamp may heat up and change resistance, so proportionality is not universal.

R=V/I; 1 Ω = 1 V/A

Put the idea to work

Worked example

A resistor carries 0.30 A when the potential difference is 9.0 V. Find its resistance.

Show the worked solution

Rearrange to R=V/I.
Substitute 9.0/0.30.
The result is measured in ohms.

Answer 30 Ω

Common mistakes

Convert milliamps to amps before calculating.
Current is not used up as it passes through a resistor.

Recall without your notes

What can you explain now?

What current flows through a 20 Ω resistor connected across 6 V?

Compare with the explanation

0.30 A

I=V/R=6/20=0.30.

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Keep learning Physics (9-1)

Check the official syllabus 2026–2028

Course scope and assessment

491 sequenced Physics lessons provide 1473 guided, independent and application problems. 58 of 58 syllabus sections have full linked teaching sequences; 0 sections remain pending. Three earlier starter overviews remain available but are not counted as full sequences. The map covers all six subject areas for 2026–2028 and keeps review and assessment limits visible. This is available content, not full programme completion, an exam grade or certified mastery. Written practice is self-checked. Supervised practical experience, cumulative assessment and human subject-teacher review remain pending. Paper method exercises do not demonstrate practical competence or complete either practical-assessment route. This is the separate 9–1 qualification 0972; Cambridge states that its 2026–2028 subject content is otherwise the same as 0625. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. The 2029 syllabus is separately published at https://www.cambridgeinternational.org/Images/764368-2029-syllabus.pdf and is not yet mapped here. This course supports exams in 2026, 2027 and 2028 only.