Question detail

A transformer is used in a relay switch circuit current-change 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

The motor effect

Question

A transformer is used in a relay switch circuit current-change 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: fluxcue422a coilcue422b fieldcue422c polecue422d gridcue422e motorcue422f generatorcue422g transformercue422h compasscue422i currentcue422j voltagecue422k forcecue422l.

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 fluxcue422a coilcue422b fieldcue422c polecue422d gridcue422e motorcue422f generatorcue422g transformercue422h compasscue422i currentcue422j voltagecue422k forcecue422l: 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 Fleming's left-hand rule (HT only), then explain how it links to a student comparing motor and generator effects and the objective to recall and apply the equation F = B x I x l for a conductor at right angles to a magnetic field.

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exam Q2: angles to a magnetic field. | The motor effect | AQA… | ExamCompanion