Numerical - Calculate value of series resistance

Q.  A 120 V d.c. shunt motor runs at speed of 1200 rpm. When the motor is operated unloaded but an additional resistance of 4 ohm is connected in series with the shunt field, then the speed increases and reaches to 1370 rpm with the same terminal voltage. The value of series resistance is

- Published on 19 Oct 15

a. 28.23 ohm
b. 32.48 ohm
c. 35.72 ohm
d. 36.82 ohm

ANSWER: 28.23 ohm

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