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A small dc motors operating at 200 V draws a current of 3 A at its full speed of 2500 r.p.m. If the resistance of the armature is $7\Omega$, the back e.m.f. of the motor is |
149 V 159 V 169 V 179 V |
179 V |
$ \xi = V - IR = 200 - 3\times 7 = 179V$ |
