A transformer has an efficiency of 80%. It works at 3 kW and 120 V. If the secondary voltage is 240 V, what will be the secondary current?

10 A

The correct answer is Option (4) → 10 A

Efficiency is given as,

efficiency = $\frac{Output\,power}{Input\,power}×100$

$⇒0.80=\frac{P_{out}}{P_{in}}$

$⇒P_{out}=0.80×300=2400W$

$∴P_{out}=v_2×I_2$

$2400=240×I_2$

$⇒I_2=10A$