A motor has coils with a resistance of 28 and operates from a voltage of 242 V.

Question

A motor has coils with a resistance of 28 and operates from a voltage of 242 V. When the motor is operating at its maximum speed, the back emf is 146 V.

(a) Find the current in the coils when the motor is first turned on.

________ A

(b) Find the current in the coils when the motor has reached maximum speed.

_________A

(c) If the current in the motor were 4.0 A at some instant, what is the back emf at that time?

_________V

An "A+ Lifesaver" will be given to whomever can answer this with details of the equations, and within the next 30 minutes. ~ Much Love, Lelani <3

Explanation / Answer

GIven resistance of the coil R =   28 voltage   V =  242 V    back emf    of motor   is     = 146 V a)    current in the coils when the motor is first turned on                   i = V /R                      = 424 / 28                     = 15.1428 A   b) current in the coils when the motor has reached maximum speed                 242 - 146 = I ( 28 )                        I = 3.428 A c)     If the current in the motor were 4.0 A at some instant,       the back emf at that time                        =   V - IR                          =    242 - 4*28                          =   130 V

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