Answer
See answers.
Work Step by Step
As discussed in section 21-13, when 120 V AC is applied to a transformer, there is an inductive reactance that effectively increases the impedance in the circuit, keeping the current at a known amount.
On the other hand, if the transformer is misused, and 120 V DC is applied to the primary, there is no induced back emf, meaning there will be much more current flowing in the primary coils. This huge current will likely overheat the coils (which contain many loops of thin, low-resistance wire), resulting in melted insulation and a short circuit.
