Introductory Physics Volume Two
Introductory Physics Volume Two
Introductory Physics Volume Two
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78 Circuits 3.10<br />
⊲ Problem 3.31<br />
Because aluminum has a greater resistivity than copper, aluminum<br />
wires heat up more than copper wires when they carry the same currents.<br />
For this reason aluminum wire of the same gauge (diameter) is<br />
rated to carry a smaller current. What current in an aluminum wire<br />
will heat up the wire the same amount as a copper wire of the same<br />
gauge carrying 20 Amps?<br />
⊲ Problem 3.32<br />
Consider the following circuit.<br />
12 kΩ<br />
9.0 V<br />
R 2 = 15 kΩ<br />
10 µF<br />
3 kΩ<br />
The switch is closed and the capacitor is allowed to charge up.<br />
(a) How much charge will there be on the capactor when it is fully<br />
charged?<br />
(b) Now the switch is opened and the charge on the capacitor drains<br />
off. How long will it take for the capacitor to reach 1/5 of the charge<br />
it had at the moment the switch was opened?
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