72 Fundamentals of Electricity and Electronics
2. Draw the symbols for the following.
a. Fixed resistor.
b. Tapped resistor.
c. Potentiometer.
Summary
1. Conductors provide a low resistance path while
insulators provide a high resistance path.
2. Four factors that affect the resistance of a conductor
are length, cross-sectional area, temperature, and
type of material.
3. A mil equals 1/1000 of an inch.
4. A circular mil equals the diameter (expressed in
mils) squared, or D2, for a round conductor.
5. Conductor insulation varies according to
application.
6. Switches are used to control the flow of electrons
through a circuit.
7. Switches are classified according to their actuator,
internal electrical circuitry (poles and throws),
ampacity, and voltage.
8. Electric lamps may use filaments or ionized gas as
a conductor.
9. Resistors are manufactured in many different ways,
and they come in fixed and adjustable packages.
10. Color codes are used to identify resistor resistance
values.
Test Your Knowledge
Do not write in this text. Place your answers on a
separate sheet of paper.
1. What is the standard unit for measuring conductor
cross-sectional areas?
2. A mil equals __________ inches.
3. A round conductor that is 1/8th inch in diameter
has a cmil area of __________.
4. Which conductor has the larger cross-sectional
area, a No. 12 or a No. 10 conductor?
5. Which conductor has more resistance per foot, a
No. 22 or a No. 6 conductor?
6. A 20-amp lighting load is connected to a 120-volt
source 300 feet away. How much voltage drop or
loss is caused by using a No. 12 aluminum wire?
(Remember that the circuit would be 600 feet long!
Also, be sure to use the aluminum wire resistance
column and not the copper column.)
7. Who is a nonprofit company that tests electrical
equipment safety features?
a. NEC
b. UL
c. NFPA
d. OSHA
8. Which organization is responsible for the study of
fire science safety and prevention?
a. NEC
b. UL
c. NFPA
d. OSHA
9. Which set of standards is used as a minimal safety
guide for the installation of electrical equipment?
a. NEC
b. UL
c. NEMA
d. OSHA
10. Which organization is a branch of the U.S. govern-
ment and is responsible for workplace safety?
a. NEC
b. UL
c. IEEE
d. OSHA
11. You would most likely use a(n) __________ for
assembling a circuit temporarily.
12. To mass produce printed circuits, a(n) __________
would be the most economical system.
13. To control a lamp from two different locations, you
would use __________ switches.
14. To open two different circuits simultaneously, you
would use __________ switches.
15. A fuse or circuit breaker provides protection from
__________.
16. Fuses and circuit breakers are rated in __________
and __________.
17. The first electric lamp had a(n) __________
filament.
18. Name three lamps that conduct through gas rather
than using a tungsten filament.
19. What keeps the current limited in a fluorescent
lamp?
20. Name four different types of resistors.
21. What are the two major classifications of film
resistors?
22. What is the film resistor substrate made of?
23. What does the numeric value 102 indicate on a
surface-mounted resistor?
24. What color code would be on a 1200 ohm, 2 watt
resistor?