Chapter 21, Problem 19Q

To determine

To explain:

The result of when $\text{120-V}$ ac input will connect to $\text{120-V}$ dc source.

Answer to Problem 19Q

Due to the higher current flow in transformer, it will burn out.

Explanation of Solution

Introduction:

When 120 Volts DC supply is applied to transformer, there is zero induced back emf that would generally occur with 120 Volts AC.

120 Volts DC encounters much less resistance as compared to the 120 Volts AC. It would cause over current to flow through transformer. Also, this large amount of the current would overheat or burn the coils, which are typically wound with numerous loops of very fine wire. This could melt the insulation and also, burn out the transformer.

Conclusion: When a transformer offers an alternating current in the place of direct current, connecting with $\text{120-V}$ voltage would result in a very higher current through the winding, that results short out the transformer.