Module 3.6-3.8 DC circuits, resistance and power
822 words · checked 2026-10-03 · Pro
These three sub-modules produce most of the Module 3 calculation questions.
Knowledge levels
| Item | A | B1 / B2 / B2L | B3 |
|---|---|---|---|
| 3.6 DC circuits: Ohm's law, Kirchhoff's laws, internal resistance | 1 | 2 | 1 |
| 3.7(a) Resistance: specific resistance, series/parallel, potentiometers, rheostats, Wheatstone bridge | — | 2 | 1 |
| 3.7(b) Resistors: PTC/NTC, colour code, tolerances, wattage, construction, thermistors, VDRs | — | 1 | — |
| 3.8 Power, work and energy | — | 2 | 1 |
Ohm's law
V = I × R - the current through a conductor is proportional to the voltage across it, at constant temperature.
| Find | Formula |
|---|---|
| Voltage | V = I R |
| Current | I = V / R |
| Resistance | R = V / I |
Worked example
A 28 V bus supplies a lamp of 14 Ω. Current = 28 / 14 = 2 A.
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