Question

1. Can a transformer be operated by a DC waveform at its input? What would be the secondary voltage of a 1:5 transformer, if a 12V DC is connected at its input?
2. Consider a transformer with a turn ratio of 2:5 that is connected to a 50-V AC source

at its primary input. What is the average power delivered to a 100 kilo-ohm resistor

connected to the secondary terminal of the of the transformer?

3. Is there a direct electrical connection between the primary and secondary terminals

of a transformer? If your answer is no, how do you explain the transfer of energy

from the primary to the secondary of the transformer?

Answer 1

Solition

1) No the transformer cannot be operated with DC input waveform. Transformers work on the principle of electromagnetic induction, the changing magnetic flux associated with a circuit will induce an e.m.f. in the circuit. So a time varying magnetic field have to be there which is produced by a time varying or alternating current or AC voltage. Thus DC voltage won't do the transformer action.

2) Zero. As we discussed transformer cannot be operated with DC voltage, even if you apply a 12V DC to the input of a transformer, there will not be any induced e.m.f in the secondary or output of the transformer.

3)

Given the turn ratio is 2:5 and input voltage of 50V AC. Thus output or secondary voltage ,

Thus there will be a output voltage 125V AC on the secondary of transformer. If this is connected to a 100kOhm resistor, average power delivered,

Thus average power delivered to the load is 0.15625 Watts.

4) & 5) No, there is no direct connection between primary and secondary coils. As we discussed in the first part transformer works in the principle of Electromagnetic induction. The magnetic flux associated with the secondary of transformer is created by the current through the primary coil. Thus any change in current in the primary coil cause an induced emf in the secondary coil. Which is nothing but the transformer action. Here the energy is getting transferred from primary circuit to secondary circuit via the magnetic field. It dosd not need any direct connection between those two.