The back emf of a motor which is just started is_________?
Correct answer: A. Zero
- A. Zero
- B. Maximum
- C. Minimum
- D. Optimum
Explanation
Back emf is produced when the motor rotates and its armature cuts magnetic flux. At the instant the motor is started, its speed is zero, so no rotational emf is induced and the back emf is 0 V. Students may choose maximum by confusing back emf with the starting current, which is actually maximum because there is no back emf to oppose the supply.
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About Faraday's Law
Faraday's law states that an induced electromotive force equals the rate of change of magnetic flux linkage through a circuit. Questions cover changing field, area, angle or motion, the negative sign associated with Lenz's law, and the distinction between induced emf and the current that may flow in a closed circuit.
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