A transformer of efficiency 90 % draws an input power of 4 kW. An electrical appliance connected across the secondary draws a current of 6 A. The impedance of the device is

Question

A transformer of efficiency 90 % draws an input power of 4 kW. An electrical appliance connected across the secondary draws a current of 6 A. The impedance of the device is (A)  60 Ω  (B)  50 Ω  (C)  80 Ω  (D)  100 Ω

Tardigrade Admin · Accepted Answer

η =(output text power/input text power)=(VSIS/4000)=(Z(IS)2/4000) ∴ (90/100)=(Z(6)2/4000) or Z=100 Ω

Q. A transformer of efficiency $90%$ draws an input power of $4 kW$ . An electrical appliance connected across the secondary draws a current of $6 A$ . The impedance of the device is

$60 Ω$

$50 Ω$

$80 Ω$

$100 Ω$

$120 Ω$

$η = \frac{o u tp u t p o w er}{in p u t p o w er} = \frac{V _{S} I _{S}}{4000} = \frac{Z ( I _{S} ) ^{2}}{4000}$
$∴$ $\frac{90}{100} = \frac{Z ( 6 ) ^{2}}{4000}$
or $Z = 100 Ω$

Q. A transformer of efficiency 90% draws an input power of 4kW. An electrical appliance connected across the secondary draws a current of 6A. The impedance of the device is

60Ω

50Ω

80Ω

100Ω

120Ω

η=inputpoweroutputpower​=4000VS​IS​​=4000Z(IS​)2​ ∴ 10090​=4000Z(6)2​ or Z=100Ω