Delmar's Standard Textbook Of Electricity
7th Edition
ISBN: 9781337900348
Author: Stephen L. Herman
Publisher: Cengage Learning
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Question
Chapter 5, Problem 1PA
To determine
The value of resistance to be used.
The power rating of the resistor.
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A small series-wound dc motor is operated from a 12-V car battery. Under a normal load, the motor draws 4.0 A, and when the armature is clamped so that it cannot turn, the motor draws 24 A. What is the back emf when the motor is operating normally?
10. What is a potent
PRACTICAL APPLICATIONS
1. You are an electrician on the job. It is decided that the speed of a large DC motor is
to be reduced by connecting a resistor in series with its armature. The DC voltage
applied to the motor is 250 V, and the motor has a full-load armature current of 50
Your job is to reduce the armature current to 40 A at full load by connecting the
resistor in series with the armature. What value of resistance should be used, and
what is the power rating of the resistor?
2. You are working on an electronic circuit. The circuit current is 5 mA. A resistor is
marked with the following bands: brown, black, red, gold. A voltmeter measures
voltage drop of 6.5 V across the resistor. Is this resistor within its tolerance rati
3. A homeowner uses a 100-watt incandescent lamp as a heater in an outside w
pump house to protect the pump from freezing in cold weather. Unfortunately
however, the lamp can burn out and leave the pump unprotected. You have b
asked to…
Q- The armature resistance of a permanent magnet dc motor is 0.80. At no load, the
motor draws 1.5 A from a supply voltage of 25 V and runs at 1500 rpm. The efficiency
of the motor while it is operating on load at 1500 rpm drawing a current of 3.5 A from
the same source will be
Chapter 5 Solutions
Delmar's Standard Textbook Of Electricity
Ch. 5 - Name three types of fixed resistors.Ch. 5 - What is the advantage of a metal film resistor...Ch. 5 - What is the advantage of a wire-wound resistor?Ch. 5 - How should tubular wire-wound resistors be mounted...Ch. 5 - A 0.5-W, 2000- resistor has a current flow of 0.01...Ch. 5 - A 1-W, 350- resistor is connected to 24 V. Is this...Ch. 5 - A resistor has color bands of orange, blue,...Ch. 5 - A 10,000- resistor has a tolerance of 5%. What are...Ch. 5 - Is 51,000 a standard value for a 5% resistor?Ch. 5 - What is a potentiometer?
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