Question:
The back emf in a dc motor is maximum
when the motor has just been switched on
When motor is switched on it has maximum speed
The back emf in a dc motor is maximum
when the motor has just been switched on
When motor is switched on it has maximum speed
Updated On: Jul 6, 2022
- If both assertion and reason are true and reason is the correct explanation of assertion
- If both assertion and reason are true but reason is not the correct explanation of assertion
- If assertion is true but reason is false
- If both assertion and reason are false
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The Correct Option is D
Solution and Explanation
Back emf is actually the induced emf produced in motor. When motor is just switched on, the magnitude of back emf is quite small due to the low speed of the motor. But the magnitude of back emf is very large at break (when electric supply fails suddenly, while the motor is running)
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Concepts Used:
Electromagnetic Induction
Electromagnetic Induction is a current produced by the voltage production due to a changing magnetic field. This happens in one of the two conditions:-
- When we place the conductor in a changing magnetic field.
- When the conductor constantly moves in a stationary field.
Formula:
The electromagnetic induction is mathematically represented as:-
e=N × d∅.dt
Where
- e = induced voltage
- N = number of turns in the coil
- Φ = Magnetic flux (This is the amount of magnetic field present on the surface)
- t = time
Applications of Electromagnetic Induction
- Electromagnetic induction in AC generator
- Electrical Transformers
- Magnetic Flow Meter