Question

Calculate the current drawn by the primary of a transformer which steps down 200 V to 20 V to operate a device of resistance 20 Ω. Assume the efficiency of transformer to be 80%.

Answer 1

V_p = 200 V, V_s = 20 V, i_s = V_s/R  = 20 V/20Ω = I A.i_p = ?

The efficiency of the transformer is