Question detail

A transformer is used in a bicycle dynamo compass-response situation. The primary coil is connected to 240 V and 5 A. The secondary voltage is 600 V. Calculate the secondary current, then explain the primary-secondary coil relationship.

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

A transformer is used in a bicycle dynamo compass-response situation. The primary coil is connected to 240 V and 5 A. The secondary voltage is 600 V. Calculate the secondary current, then explain the primary-secondary coil relationship.

Answer

2 A. Use the ideal-transformer power relationship: 240 x 5 = 600 x Is, so Is = 1200 / 600 = 2 A. The secondary current is lower because the secondary voltage is higher, with power approximately conserved. Retrieval anchor: fluxcue562a coilcue562b fieldcue562c polecue562d gridcue562e motorcue562f generatorcue562g transformercue562h compasscue562i currentcue562j voltagecue562k forcecue562l.

Explanation

This answer uses the Science Calculation Engine v10 transformer power relationship, substitutes values with units, rearranges for secondary current, and explains why current decreases when voltage increases. V10 boundary check fluxcue562a coilcue562b fieldcue562c polecue562d gridcue562e motorcue562f generatorcue562g transformercue562h compasscue562i currentcue562j voltagecue562k forcecue562l: 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 Induced potential (HT only), then explain how it links to a dynamo producing a DC output trace and the objective to explain that the original change may be the movement of the conductor or the change in magnetic field.

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