Assertion (A): A transformer cannot work on D.C. supply.
Reason (R): D.C. changes neither in magnitude nor in direction.
1. Both A & R are true and the (R) is the correct explanation of the (A)
2. Both A & R are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Transformers rely on mutual induction, which requires a changing magnetic flux. DC current, being constant (R), produces a steady flux, thus no induced EMF. Both A and R are true, and R correctly explains A.
Assertion (A): If we use a battery across the primary of a step up transformer, no voltage is obtained across secondary.
Reason (R): Battery gives a steady current.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
Assertion (A) is true. Transformers require a changing magnetic flux to induce voltage. Reason (R) is true; a battery provides DC current. This steady current causes constant flux, hence no induced emf in the secondary. (R) correctly explains (A).