Problems 371
12.22.Contact your electric utility company and obtain infor-
mation on what the company charges for each kilowatt
hour usage. Estimate the cost of your electric power
consumption for a typical day. Make a list of your
activities for the day and estimate the power consump-
tion for the devices that you used. Write a brief report
discussing your findings.
12.23.For Example 12.6, we computed the total current
drawn by the circuit. Determine the current in each
branch of the circuit given in Example 12.6.
12.24.For an automobile battery, investigate what is meant by
the following terms: ampere-hour rating, cold-cranking
rating, and reserve capacity rating. Write a brief report
discussing your findings.
12.25.For a primary cell such as an alkaline battery, what does
the term amp-hour represent? Gather information on
the amp-hour rating for some alkaline batteries. Write
a one-page summary of your findings.
12.26.As you know, a fuse is a safety device that is commonly
placed in an electrical circuit to protect the circuit
against excessive current. Investigate the various types
of fuses, their shapes, materials, and sizes. Write a brief
report discussing your findings.
12.27.There are many different types of capacitors, includ-
ing ceramic, air, mica, paper, and electrolytic. Investi-
gate their usage in electrical and electronic applications.
Write a brief report discussing your findings.
12.28.In class, you are given three items: a battery, a light
bulb, and a piece of wire. Make a flashlight using these
items.
12.29.According to Sylvania, a light-bulb manufacturer, its
40-W CFL light consumes 9 watts and produces
495 lumens. What is the efficacy for this light?
12.30.Calculate the efficacy for the following lights: (a) Syl-
vania accent LED light, which uses 2 watts and pro-
duces 60 lumens, and (b) Sylvania 40-W CFL, which
uses 9 watts and produces 495 lumens.
12.31.The Sylvania Super Saver 75-W light uses 20 watts,
produces 1280 lumens, and costs $4.49. As an alter-
native, a generic 75-W-incandescent light bulb costs
$0.40, produces 1200 lumens, and has a service life of
750 hours. Compare the performance of each light by
calculating the efficacy for each light and estimate howmuch it would cost to run each light for 4 hours per
day for 300 days in a year. Assume electricity costs
9 cents per kWh.
12.32.There are a number of ways that you can reduce the
energy waste associated with lighting systems. One way is
to make use of smart controllers and use devices such as
lighting-dimmer controls, lighting-motion-sensor con-
trols, lighting-occupancy controls, lighting-photosensor
controls, and lighting-timer controls. Write a brief report
describing how these various types of lighting controllers
work and give examples of their usage.
12.33.Visit the lighting section of a hardware store and look
up the following information for comparable incan-
descent bulb, CFL, and LED lights. Read the manu-
facturer’s ratings on the packaging and record lumens,
light source color temperature, and power consump-
tion in terms of watts. Write a brief report discussing
your findings.
12.34.Perform a lighting energy audit for your classroom.
First, define the space characteristics by recording the
length, width, and the height of your classroom. Next,
obtain information about the type of lighting system,
the number of light sources, and their controls. Also,
obtain information about the occupancy profile — that
is the number of people every hour using the class-
room. Calculate the watts /ft
2
for the classroom as a
function of time. Write a brief report to your instruc-
tor discussing your findings. Suggest ways the lighting
energy consumption for your classroom may be
improved.
12.35.This is a class project. You are to perform a lighting
energy audit for your indoor sport arena. Collect infor-
mation about the arena size, occupancy profile — that
is the number of people every 15 minutes or 30 min-
utes using the facility. Also, obtain information about
the lighting systems (fluorescent, incandescent, Mer-
cury vapor, sodium, Metal Halide, and other systems)
and controlling devices used in the space. Calculate the
watts /ft
2
for the space as a function of time. Write a
brief report to your instructor discussing your findings.
Suggest ways the lighting energy consumption may be
improved.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