Question

A step down transformer connected to an ac mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit?

Options

• 4 A

• 0.2 A

• 0.4 A

• 2 A

Answer 1

0.2 A

Explanation:

Given, V_p = 220V, P_s = 44W

As there is no power loss, so Input power = Output power

⇒ V_pI_p = V_sI_s = P_s

⇒ 220 × I_p = 44

⇒ I_p = \[\frac {44}{220}\]

⇒ I_p = \[\frac {2}{10}\] = 0.2 A