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
Answer: Option C
This Question Belongs to Electrical Engineering >> Transformers
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The purpose of providing an iron core in a transformer is to
A. provide support to windings
B. reduce hysteresis loss
C. decrease the reluctance of the magnetic path
D. reduce eddy current losses
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
If the percentage impedances of the two transformers working in parallel are different, then
A. transformers will be overheated
B. power factors of both the transformers will be same
C. parallel operation will be not possible
D. parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load
An ideal transformer will have maximum efficiency at a load such that
A. copper loss = iron loss
B. copper loss < iron loss
C. copper loss > iron loss
D. none of the above
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.