Question

A 60 W load is connected to the secondary of a transformer whose primary draws line voltage. If a current of 0.54 A flows in the load, what is the current in the primary coil? Comment on the type of transformer being used.

Answer 1

Suppose $V_S,I_S$ and $V_P,I_P$ are voltages and current of the secondary and primary of the transformer respectively.

Given,

$P_s=60W$

$I_s=0.54A$

$V_p=220V$

$\therefore V_s=\frac{P_S}{I_s}=600.54=111V$

Voltage in the secondary is less than voltage in the primary. Therefore, the transformer is step down transformer.

Since, the transformation ratio,

$\frac{V_s}{V_p}=\frac{I_p}{I_s}$ (For an ideal transformer)

$\therefore I_p=\frac{V_s}{V_p}\times I_s=111220\times 0.54=0.27A$

Final Answer: 0.27 A