Question detail
In a split-ring motor kit cause 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 split-ring motor kit cause 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: fluxcue716a coilcue716b fieldcue716c polecue716d gridcue716e motorcue716f generatorcue716g transformercue716h compasscue716i currentcue716j voltagecue716k forcecue716l.
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 fluxcue716a coilcue716b fieldcue716c polecue716d gridcue716e motorcue716f generatorcue716g transformercue716h compasscue716i currentcue716j voltagecue716k forcecue716l: 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 dynamo producing a DC output trace and the objective to explain how the effect of an alternating current in one coil inducing a current in another is used in transformers.
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