Question detail
In a power-station transformer load-effect 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.
At a glance
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Topic
Induced potential, transformers and the National Grid (physics only) (HT only)
Question
In a power-station transformer load-effect 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: fluxcue611a coilcue611b fieldcue611c polecue611d gridcue611e motorcue611f generatorcue611g transformercue611h compasscue611i currentcue611j voltagecue611k forcecue611l.
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 fluxcue611a coilcue611b fieldcue611c polecue611d gridcue611e motorcue611f generatorcue611g transformercue611h compasscue611i currentcue611j voltagecue611k forcecue611l: 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 motors and generators
Treating motors and generators as interchangeable when answering about National Grid transformer reasoning.
Instead, identify the exact Unit 4.7 idea in Uses of the generator effect (HT only), then explain how it links to a steel core electromagnet demonstration and the objective to explain how the generator effect is used in an alternator to generate ac.
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