Question detail

In a moving-wire motor effect diagnosis demonstration, a transformer has 500 primary turns and 100 secondary turns. The primary potential difference is 240 V. Calculate the secondary potential difference and identify whether it is step-up or step-down.

Try the question, check the answer, then read the explanation to understand the curriculum point.

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Topic

Induced potential, transformers and the National Grid (physics only) (HT only)

Question

In a moving-wire motor effect diagnosis demonstration, a transformer has 500 primary turns and 100 secondary turns. The primary potential difference is 240 V. Calculate the secondary potential difference and identify whether it is step-up or step-down.

Answer

48 V. Use the transformer voltage ratio: 240 / Vs = 500 / 100, so Vs = (240 x 100) / 500 = 48 V. The secondary coil has fewer windings, so this is step-down. Retrieval anchor: fluxcue841a coilcue841b fieldcue841c polecue841d gridcue841e motorcue841f generatorcue841g transformercue841h compasscue841i currentcue841j voltagecue841k forcecue841l.

Explanation

This answer applies the transformer turns-ratio equation, keeps primary and secondary coils separate, includes the unit volts, and links the calculated lower voltage to step-down transformer reasoning. V10 boundary check fluxcue841a coilcue841b fieldcue841c polecue841d gridcue841e motorcue841f generatorcue841g transformercue841h compasscue841i currentcue841j voltagecue841k forcecue841l: in the motor effect, the force is perpendicular to the current and magnetic field; in a generator, relative motion or a changing magnetic field induces a potential difference or induced current; outside a magnet, magnetic field lines go from north to south; AC alternating current changes direction, while DC direct current flows in one direction and needs a commutator in a DC generator context.

Common mistake

National Grid transformer reasoning: avoid magnetic field...

Treating magnetic field direction and force direction as interchangeable when answering about National Grid transformer reasoning.

Instead, identify the exact Unit 4.7 idea in Transformers (HT only), then explain how it links to a steel core electromagnet demonstration and the objective to recognise that transformer equations are given on the Physics equation sheet.

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