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Difficulty: MediumElectromagnetism and Induction

In an alternating current (AC) generator, increasing the rotational speed of the armature coil within a constant magnetic field increases the output frequency but has no effect on the magnitude of the peak induced electromotive force (EMF).

Answer: Answer

Answer

False
The statement is false because induced electromotive force depends directly on how fast the magnetic field lines are cut. Spinning the armature coil faster increases both the frequency of the alternating current and the peak induced voltage.

Step-by-Step Solution

1
Identify the relationship between rotational speed and AC frequency in a generator.
Higher rotational speed increases the number of electrical cycles completed per second, directly increasing frequency (ff).
Each mechanical revolution corresponds to a fixed number of electrical cycles based on the generator's pole pairs.
2
Apply Faraday's Law of Electromagnetic Induction to determine how rotational speed affects induced voltage amplitude.
Faster rotation increases the angular velocity (ω\omega), causing magnetic flux lines to be cut more rapidly over time (ΔΦΔt\frac{\Delta \Phi}{\Delta t}).
Faraday's Law states that induced electromotive force is directly proportional to the rate of change of magnetic flux (Epeak=NBAωE_{\text{peak}} = N B A \omega).
3
Evaluate the statement based on the combined physical effects.
Since rotational speed increases both output frequency and peak induced EMF, the claim that peak EMF remains unaffected is incorrect.
A generator produces higher peak voltage when spun faster because conductor velocity through the magnetic field increases.

Key Concept

Faraday's Law of Electromagnetic Induction in AC Generation
Estimated Time:1m 0s
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Topics

Electromagnetism and Induction

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