ent BACK NEX PRINTER VERSION Chapter 22, Problem 40 A 120.0-V motor draws a curr

Question

ent BACK NEX PRINTER VERSION Chapter 22, Problem 40 A 120.0-V motor draws a current of 7.98 A when running at normal speed. The resistance of the armature wire is 0.799o (a) Determine the back emf generated by the motor (b) what is the current at the instant when the motor is just turned on and has not begun to rotate? (c) What series resistance must be added to limit the starting current to 15.0 A (a) Number Units Units Units (b) Number (c) Number by accessing this Question Assistance, you will learm while you earn points based on the Poine Potential Policy set by your instructor Question Attempts: Unlimited AE FOR LATER SUBHET ANSWER Earm Maximum Points availabie only i you question eorrectly in four attempts or less.

Explanation / Answer

a) back emf = V - I R

= 120.0 - (7.98 * 0.799)

back emf = 113.6 V

b) back emf = V - I R

0 = V - I R

V = I R

I = V / R = 120 / 0.799

current = 150.2 A

c) R = (120.0 / 15.0) - (0.799)   

series resistance = 7.20 ohms

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