Q.13 Establish the condition to get wattless current in an ac circuit.

Dear Student 

The condition to get wattless current is having inductive and/or capacitive circuit i.e. Resistance in the circuit must be zero. In such case the power dissipated in the circuit would be zero . Hence wattless circuit. The power factor will be zero.
as Power factor = $\frac{real power(in watts)}{apparant power(Volt-amps)}$ and real power is zero here.

Regards