Question

The primary coil of a transformer is connected to a 120 v wall outlet. the secondary coil is connected to a lamp that dissipates 60 w. what is the nns current in the primary coil?

Answer 1

Energy/power is not gained or lost going through a (ideal) transformer.

So the transformer in this problem really doesn't matter. If the lamp is using energy at the rate of 60 watts, then the whole contraption is getting 60 watts of power from the wall outlet.

Power = (voltage) x (current)

60 watts = (120 v) x (current)

Current = (60 watts) / (120 v)

Current = 0.5 Ampere