370 Chapter 12 Electric Current and Related Parameters
I 4 =?
I 2 = 1 A
I 1 = 1 A I 3 = 0.5 A
Problem 12.20
12 V
R 1 = 9
R 3 = 6
R 2 = 9
Problem 12.18
12 V
R 1 = 6 R 2 = 3 R 3 = 6
Problem 12.19
12.12. When subjected to pressure, certain materials create
a relatively small voltage. Materials that behave in
this manner are called piezoelectrics. Investigate the
applications in which piezoelectrics are used. Write a
brief report discussing your findings.
12.13. Prepare an electrical circuit plan similar to the one
shown in Figure 12.9 for your apartment, your home,
or a section of your dormitory.
12.14. The National Electrical Code (NEC) covers the safe
and proper installation of wiring, electrical devices, and
equipment in private and public buildings. NEC is
published by the National Fire Protection Asso-
ciation (NFPA) every three years. As an example of
an NEC provision, the receptacle outlets in a room
in a dwelling should be placed such that no point
on the wall space is more than 6 ft away from the
outlet in order to minimize the use of extension
cords. After performing a Web search or obtaining a
copy of the NEC handbook, give at least three other
examples of National Electric Codes for a family
dwelling.
12.15. Obtain a multimeter (voltmeter, ohm, and current
meter) and measure the resistance and the voltage of
the heating element in the back window of a car.
Determine the power output of the heater.
12.16. Visit a hardware store and obtain information on the
sizes of heating elements used in home hot water
heaters. If a hot water heater is connected to a line with
240 V, determine the current drawn by the hot water
heater and its power consumption.
12.17. As explained in this chapter, the National Electrical
Code gives specific information on the type of wires
used for general wiring. Perform a search and obtain
information on wire types, maximum operating tem-
peratures, insulating materials, outer cover sheaths, and
usage types. Prepare a table that shows examples
of these codes; show wire size, temperature rating,
application provisions, insulation, and outer covering.
12.18. Determine the total resistance and the current flow for
the circuit shown in the accompanying figure.
12.19. Determine the total resistance and the current flow in
each branch for the circuit shown in the accompanying
figure.
12.20.Use Kirchhoff ’s current law to determine the missing
current in the circuit shown in the accompanying
figure.12.21.Obtain a flashlight and a voltmeter. Measure the resis-
tance of the light bulb used in the flashlight. Draw the
electrical circuit for the flashlight. Estimate the current
drawn by the light when the flashlight is on.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