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# A transformer cannot raise or lower the voltage of a D.C. supply because

A. There is no need to change the D.C. voltage

B. A D.C. circuit has more losses

C. Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero

D. None of the above

This Question Belongs to Electrical Engineering >> Transformers

1. An AC changes its direction at every cycle. Due to change in direction of current, the direction of flux created by the current also changes.
On the other hand, DC supply does not change its direction and hence flux also does not change.
According to Faraday's law of induction, when flux changes only then it links with the secondary and induces emf. Induced emf is directly proportional to change of the flux. So no current or voltage is obtained in the secondary in case of DC supply.

Related Questions on Transformers

A good voltage regulation of a transformer means

A. output voltage fluctuation from no load to full load is least

B. output voltage fluctuation with power factor is least

C. difference between primary and secondary voltage is least

D. difference between primary and secondary voltage is maximum