A transformer having efficiency 90% is working on 100 V and at 2.0 kW power. If the current in the secondary coil is 5A, calculate the current in the primary coil…

Q: A transformer having efficiency 90% is working on 100 V and at 2.0 kW power. If the current in the secondary coil is 5 A, calculate (i) the current in the primary coil and (ii) voltage across the secondary coil.

Sol: Here , η = 90% = 9/10, Is = 5 A , Ep = 100 V,

(i) Ep Ip = 2 kW = 2000 W

Ip = 2000/Ep or Ip = 2000/100 = 20 A

(ii) $\large \eta = \frac{Output \; Power}{Input \; Power}$

$\large \eta = \frac{E_s I_s}{E_p I_p}$

Es Is = η × Ep Ip

Es Is = (9/10) × 2000 = 1800 W

Es = 1800 /Is = 1800/5

Es = 360 volt