Homework Help: Physics

Posted by Mary on Tuesday, October 9, 2007 at 3:28pm.

A 120.0 volt motor draws a current of 7.60 A when running at normal speed. The resistance of the armature wire is 0.610.

(a) Determine the back emf generated by the motor.

115.364 V

(b) What is the current at the instant when the motor is just turned on and has not begun to rotate?

196.72A

(c) What series resistance must be added to limit the starting current to 15.0 A?

(a) and (b) answers are both correct. I am having a problem figuring out (c). Please help!

Physics - bobpursley, Tuesday, October 9, 2007 at 3:40pm
If you want to limit starting current to 15 amp, then

15= 120/(.610+R)

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