Question detail

A transformer is used in a National Grid substation turns-ratio 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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The motor effect

Question

A transformer is used in a National Grid substation turns-ratio 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: fluxcue492a coilcue492b fieldcue492c polecue492d gridcue492e motorcue492f generatorcue492g transformercue492h compasscue492i currentcue492j voltagecue492k forcecue492l.

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 fluxcue492a coilcue492b fieldcue492c polecue492d gridcue492e motorcue492f generatorcue492g transformercue492h compasscue492i currentcue492j voltagecue492k forcecue492l: 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

motor-effect force direction: avoid motors and generators

Treating motors and generators as interchangeable when answering about motor-effect force direction.

Instead, identify the exact Unit 4.7 idea in Loudspeakers (physics only) (HT only), then explain how it links to a step-down transformer for a low-voltage device and the objective to state that loudspeakers and headphones use the motor effect.

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exam Q2: headphones use the motor effect. | The motor effect | AQA… | ExamCompanion