Question

.5 ohm resistance is connected across the 120 V secondary winding of a step down transformer if the primary curtain is 6 A what is the primary voltage?

Answer 1

Assuming an ideal transformer (no losses):

Secondary current Is = Vs / R = 120 V / 0.5 Ω = 240 A.

For an ideal transformer Vp = Vs * (Is / Ip) = 120 * (240 / 6) = 120 * 40 = 4800 V.

So the primary voltage is 4.8 kV.