Question

The armature of a dc motor has 15 $\Omega$ resistance. It draws a current of 1.6 A when run by 220 V dc supply. The value of back emf will be:

• A. 24 V
• B. 196 V
• C. 220 V
• D. 244 V

Answer 1

The correct option is B 196 V

Let back emf be $V^{\prime }$ and emf of supply =$V$

Applying Kirchoff's loop law in the circuit:

$V+V^{\prime }-IR=0$

$⟹V^{\prime }=-(V-IR)$

Hence, Back emf=$V-IR$

$=220-1.6\times 15$

Back emf$=196V$

Answer-(B)