A transformer has 1000 turns in the primary and 2000 turns in its secondary winding. The primary voltage is 200 V and the load across the secondary is \( 100\,\Omega \). If the transformer is assumed to be ideal, then the value of current in the primary is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 8.0 A
In a transformer the voltages are in the ratio of the turns. In an ideal transformer there is no loss, so the input power equals the output power.
\( \displaystyle V_s = V_p\,\frac{N_s}{N_p} = 200\,\mathrm{V} \times \frac{2000}{1000} = 400\,\mathrm{V} \)
\( \displaystyle I_s = \frac{V_s}{R} = \frac{400\,\mathrm{V}}{100\,\Omega} = 4\,\mathrm{A} \)
\( \displaystyle V_p I_p = V_s I_s \;\Rightarrow\; I_p = \frac{V_s I_s}{V_p} = \frac{400 \times 4}{200} = 8\,\mathrm{A} \)