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 ?

The correct option is 0.2 A.

To find the current in the primary circuit, we can apply the principle of conservation of energy to the transformer.

For an ideal transformer where power losses are ignored, the input power in the primary circuit ($P_p$) is exactly equal to the output power in the secondary circuit ($P_s$):

$P_p=P_s$

We are given the following parameters from the problem:
Primary voltage, $V_p=220\text{V}$
Secondary voltage, $V_s=11\text{V}$
Power in the secondary circuit (power consumed by the lamp), $P_s=44\text{W}$

Since there are no power losses, the power in the primary circuit is:
$P_p=44\text{W}$

The electrical power in the primary circuit is also given by the formula:
$P_p=V_p\times I_p$
where $I_p$ is the current in the primary circuit.

Substituting the known values into the equation:
$44=220\times I_p$

Now, solving for $I_p$:
$I_p=\frac{44}{220}$
$I_p=0.2\text{A}$

Thus, the current in the primary circuit is 0.2 A.