An ideal transformer steps down 220 V to 22 V and delivers a current of 0.1 A from its secondary. The current drawn from the primary is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 0.01 A
An ideal transformer has no energy losses. So the power drawn by the primary equals the power delivered by the secondary, \( V_pI_p=V_sI_s \). A step-down transformer lowers the voltage and raises the current in the same ratio. So the primary current is the smaller one.
\( \begin{aligned} I_p &= \frac{V_sI_s}{V_p} \\ &= \frac{22\,\mathrm{V}\times0.1\,\mathrm{A}}{220\,\mathrm{V}} \\ &= 0.01\,\mathrm{A} \end{aligned} \)