16A
YOUR ANSWER:
The specific resistance of a material is the resistance of a unit volume of
(From P1-21A)
of that material at a temperature of 20 degrees centigrade.
Outstanding. The unit volume for metallic conductors is a conductor one foot long and one mil (.001
inch) in diameter and the unit volume for nonmetallic conductors is a cube one centimeter long and one
centimeter wide.
Now that we know all about resistance, lets go into some of the things that affect the selection of the
conductor we use. There are many different applications for conductors. Sometimes we simply want a conductor
to provide a low-resistance path for electrons to travel around the circuit. At other times, we might want the
conductor to offer fairly high resistance so that it will heat; up for example, toasters, electric heaters, and
soldering irons. At other times, we might require elasticity (good spring action) and there is always the big item,
COST. The five items that we will consider when selecting a conductor are: cost, ability to be fused or soldered,
melting point, weight, and elasticity.
Is the following statement true or false?
The first consideration when choosing a conductor is to use a
material that has the lowest specific resistance.
True.
Page 1-14A
False.
Page 1-20B
16B
YOUR ANSWER:
The length and the cross-sectional area.
(From P1-3B)
You have the right idea, but you didn't go quite far enough.
Remember, we said that there are four factors which determine the resistance of a conductor. They are
the type of material used, the length, the cross-sectional area, and the temperature. Now, go back to Page 1-3B
and read the question again.
IT0340
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