Q4.Which of the following are reasons why brushes are made of carbon?(a) Carbon is a good conductor(b) Carbon will wear and confirm to the shape of the commutator(c) Carbon will form a low friction surface with the commutator(d) Carbon will wear before and prevent damage to the commutator(e) All of the above.Q5.Why is an external resistor required to bring a DC motor up to speed?(a) To increase the motor starting torque(b) To decrease the motor starting torque(c) To limit the motor starting current(d) To dynamically brake the motor(e) All of the aboveQ6.Why are the magnetic cores of rotating machines constructed from laminated steel?(a) To reduce copper losses(b) To reduce hysteresis loss(c) To reduce eddy current losses(d) To reduce eddy current and hysteresis losses(e) All of the aboveWhich of the following generators best fits the description of a "constant current"generator?Q7.(a) DC series generator(b) DC separately-excited shunt generator(c) DC self-excited shunt generator(d) DC differential compound generator(e) DC cumulative compound generator

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Q4. Which of the following are reasons why brushes are made of carbon? (a) Carbon is a good conductor (b) Carbon will wear and confirm to the shape of the commutator (c) Carbon will form a low friction surface with the commutator (d) Carbon will wear before and prevent damage to the commutator (e) All of the above.

Q4. Which of the following are reasons why brushes are made of carbon? (a) Carbon is a good conductor (b) Carbon will wear and confirm to the shape of the commutator (c) Carbon will form a low friction surface with the commutator (d) Carbon will wear before and prevent damage to the commutator (e) All of the above.

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter5: Resistors

Section: Chapter Questions

Problem 1PA

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