Question

A step down transformer is connected to main supply 200V to operate a 6V, 30W bulb. The current in primary is

• A. 3 amp
• B. 1.5 amp
• C. 0.3 amp
• D. 0.15 amp

Answer 1

Answer: (D)

0.15 amp

Answer 2

$V_{p} = 200V,$ $V_{s} = 6V$̃ $P_{out} = V_{s}i_{s}$ ̃ 30 = 6 ´ i_s

̃ i_s = 5A

From $\frac{V_{s}}{V_{p}} = \frac{i_{p}}{i_{s}}$ ̃ $\frac{6}{200} = \frac{i_{p}}{5}$ ̃ $i_{p} = 0.15A$