Question detail
A transformer is used in a relay switch circuit boundary 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.
At a glance
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Topic
Induced potential, transformers and the National Grid (physics only) (HT only)
Question
A transformer is used in a relay switch circuit boundary 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: fluxcue758a coilcue758b fieldcue758c polecue758d gridcue758e motorcue758f generatorcue758g transformercue758h compasscue758i currentcue758j voltagecue758k forcecue758l.
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 fluxcue758a coilcue758b fieldcue758c polecue758d gridcue758e motorcue758f generatorcue758g transformercue758h compasscue758i currentcue758j voltagecue758k forcecue758l: 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 primary and secondary...
Treating primary and secondary coils 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 bar magnet and plotting compass practical and the objective to describe a step-down transformer as having secondary potential difference less than primary potential difference.
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