Question detail

In a coil-and-galvanometer induction AC-output 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 coil-and-galvanometer induction AC-output 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: fluxcue526a coilcue526b fieldcue526c polecue526d gridcue526e motorcue526f generatorcue526g transformercue526h compasscue526i currentcue526j voltagecue526k forcecue526l.

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 fluxcue526a coilcue526b fieldcue526c polecue526d gridcue526e motorcue526f generatorcue526g transformercue526h compasscue526i currentcue526j voltagecue526k forcecue526l: 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 AC and DC

Treating AC and DC as interchangeable when answering about National Grid transformer reasoning.

Instead, identify the exact Unit 4.7 idea in Induced potential (HT only), then explain how it links to a bar magnet and plotting compass practical and the objective to describe how a potential difference is induced across a conductor when the conductor moves relative to a magnetic field.

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