Problems 369
Summary
Now that you have reached this point in the text
- You should understand the importance of electricity and electrical power in our every-
day lives. - You should know what is meant by electric current and the difference between direct current
and alternating current. - You should have an idea about various sources of electricity.
- You should understand the concept of electrical resistance and its unit.
- You should be familiar with the AWG wire designations.
- You should be familiar with the role of electric motors in our everyday lives.
- You should be familiar with lighting terminology.
Problems
12.1. How are batteries connected in the following products:
a hand-held calculator such as a TI 85, a flashlight, and
a portable radio? Are the batteries connected in a series
arrangement or in a parallel arrangement?
12.2. Identify the types of batteries used in the following
products:
a. a laptop computer
b. an electric shaver
c. a cordless drill
d. a camcorder
e. a cellular phone
f. a flashlight
g. a wristwatch
h. a camera
12.3. Investigate the size and the material used for heating
elements in the following products: a toaster, hair
dryer, pressing iron, coffeemaker, and an electric
stovetop.
12.4. As explained in this chapter, potentiometers (rheostats)
are used in applications to adjust the electric current
in a circuit. Investigate the different types of resistance
element used for various applications. The resistance
element of the rheostat is typically made from metal
wires or ribbons, carbon, or a conducting liquid. For
example, in applications where the current in the cir-
cuit is relatively small, the carbon type is used. Write a
brief report discussing your findings.
12.5. Electrical furnaces are used in the production of steel
that is consumed in the structural, automotive, tool,and aircraft industries in the United States. Electrical
furnaces are typically classified into resistance furnaces,
arc furnaces, and induction furnaces. Investigate the
operation of these three types of furnaces. Write a brief
report describing your findings.
12.6. Identify examples of motors used in a new automobile.
For example, a motor is used to run the fan that deliv-
ers warm or cold air into the car.
12.7. Obtain information about the electric current and volt-
age ratings of your own residential building or a build-
ing belonging to someone you know. If possible draw
a diagram showing the power distribution, similar to
Figure 12.7.
12.8. What is the current that flows through each of the fol-
lowing light bulbs: 40 W, 60 W, 75 W, 100 W? Each
light is connected to a 120-V line.
12.9. If a 1500-W hair dryer is connected to a 120-V line,
what is the maximum current drawn?
12.10. Refering to Table 12.1, create a table that shows the
relative resistance of 1-ft-long wires having diameters of
1 mil made of the metals given in Table 12.1 to
1-ft-long copper with a diameter of 1 mil. For example,
using the data given in Table 12.1, the relative resis-
tance of 1-foot-long, 1-mil-diameter aluminum wire
to 1-ft-long, 1-mil copper wire is 1.64 (17.01 /
10.371.64).
12.11. Investigate how an alkaline battery and an automobile
maintenance-free battery (lead acid, gel cell) work.
Write a brief report discussing your findings.Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀