A 220 volts input is supplied to a transformer. The output circuit draws a current of 2.0 ampere at 440 volts. If the efficiency of the transformers is 80%, the current drawn by the primary windings of the transformer is

Options

(a) 3.6 ampere
(b) 2.8 ampere
(c) 2.5 ampere
(d) 5.0 ampere

Correct Answer:

5.0 ampere

Explanation:

V₂ / V₁ = 0.8 I₁ / I₂
V₂I₂ / V₁I₁= 0.8
V₁ = 220 V, I₂ = 2.0 A, V₂ = 440 V
I₁ = V₂I₂ / V₁ x 10/8 = 440 x 2 x 10 / 220 x 8
= 5.0 A