Question detail

A transformer is used in a bicycle dynamo evidence 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 evidence 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: fluxcue730a coilcue730b fieldcue730c polecue730d gridcue730e motorcue730f generatorcue730g transformercue730h compasscue730i currentcue730j voltagecue730k forcecue730l.

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 fluxcue730a coilcue730b fieldcue730c polecue730d gridcue730e motorcue730f generatorcue730g transformercue730h compasscue730i currentcue730j voltagecue730k forcecue730l: 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 step-up transformer on the National Grid and the objective to recall and apply the transformer equation Vp / Vs = np / ns.

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