Page 47 - Teach Yourself Electricity and Electronics

Resistance and the ohm 27

Table 2-1. Resistivity for copper wire,
in terms of the size in American
Wire Gauge (AWG).

Wire size, AWG Resistivity, ohms/km
2 0.52
4 0.83
6 1.3
8 2.7
10 3.3
12 5.3
14 8.4
16 13
18 21
20 34
22 54
24 86
26 140
28 220
30 350

deliver an unlimited number of charge carriers, there will be a current of 1A. If the re-
sistance is doubled, the current is cut in half. If the resistance is cut in half, the current
doubles. Therefore, the current flow, for a constant voltage, is inversely proportional
to the resistance. Figure 2-3 is a graph that shows various currents, through various re-
sistances, given a constant voltage of 1V across the whole resistance.

2-3 Current versus resistance
through an electric device
when the voltage is
constant at 1 V.