DC CIRCUIT TERMINOLOGY
Basic DC Theory
TABLE 2
Temperature Coefficients for Various Materials
Temperature
Material
Coefficient, W per °C
Aluminum
0.004
Carbon
-0.0003
Constantan
0 (avg)
Copper
0.004
Gold
0.004
Iron
0.006
Nichrome
0.0002
Nickel
0.005
For a given material, a may vary with temperature; therefore, charts are often used to describe
how resistance of a material varies with temperature.
An increase in resistance can be approximated from equation (2-2).
(2-2)
Rt
Ro
Ro(aDT)
where
Rt
=
higher resistance at higher temperatures
Ro
=
resistance at 20oC
a
=
temperature coefficient
DT
=
temperature rise above 20oC
Electric Circuit
Each electrical circuit has at least four basic parts: (1) a source of electromotive force,
(2) conductors, (3) load or loads, and (4) some means of control. In Figure 13, the source of
EMF is the battery; the conductors are wires which connect the various component parts; the
resistor is the load; and a switch is used as the circuit control device.
ES-02
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