Question

An electric motor operating on 50 volt D.C. supply draws a current of 10 amp. If the efficiency of motor is `40%` then the resistance of the winding of the motor is
A. `1.5Omega`
B. `3Omega`
C. `4.5Omega`
D. `6Omega`

Answer 1

Correct Answer - B
Input power `P=VI=50xx10`
power dissipated as heat `I^(2)R=100R`
`"Efficiency"=("output power")/("input power")`
`(40)/(100)=(500-100R)/(500)`