Question detail

In a step-down charger transformer application 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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Induced potential, transformers and the National Grid (physics only) (HT only)

Question

In a step-down charger transformer application 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: fluxcue786a coilcue786b fieldcue786c polecue786d gridcue786e motorcue786f generatorcue786g transformercue786h compasscue786i currentcue786j voltagecue786k forcecue786l.

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 fluxcue786a coilcue786b fieldcue786c polecue786d gridcue786e motorcue786f generatorcue786g transformercue786h compasscue786i currentcue786j voltagecue786k forcecue786l: 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 an alternator producing an AC output trace and the objective to recall and apply the equation Vp x Ip = Vs x Is for a 100 percent efficient transformer.

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