Physics Problem

Question

The 400-turn primary coil of a step-down transformer is connected to an ac line that is 120 V (rms). The secondary coil is to supply 15.0 A at 6.30 V (rms).

1)Assuming no power loss in the transformer, calculate the number of turns in the secondary coil.

2)Assuming no power loss in the transformer, calculate the current in the primary coil.

Answer 1

1. Use the relationship that the secondary voltage = the primary voltage times the ratio of the # turns in the secondary divided by the # turns in the primary.
2. Since the problem says that no power is lost in this ideal transformer set the power supplied to the primary equal to the power transferred to the secondary. Recall that electrical power is the product of the current times the voltage.