Homework 3
Due: Monday, August 29
1
(a) Assuming that the relative resistivity of nickel with respect to copper is 5.1, and
the absolute resistivity of copper at room temperature is 1.7×108Ω·cm, find the
resistance of a nickel ribbon with the following dimensions: length of 40 m, width of
1.5 cm, and thickness of 0.1 cm.
(b) Compute the resistance of 600 feet of 14-gauge1copper wire (2.575 Ω/100 ft)
(c) Repeat (b) for 400 feet of 14-gauge nickel wire.
(d) If one end of the copper wire from (b) is soldered to one end of the nickel wire
from (c), find the total resistance of the 1000 feet of wire.
2
For the circuit of Figure 1 assume that R= 1 Ω, and the input current to the circuit
is is(t) = 200 sin(10πt) mA for t > 0 and zero for t < 0. Compute the instantaneous
power delivered by the source. Using a graphing program, plot the power delivered
as a function of time for 0 <t<1 sec.
2 R 3 R
5 R
is(t)
Friday, August 26, 2011
Figure 1: Model circuit
1American wire gauge, also known as the Brown & Sharpe wire gauge, is a standardized
wire gauge system used since 1857 predominantly in the United States and Canada for the di-
ameters of round, solid, nonferrous, electrically conducting wire. You can read more on this at
http://en.wikipedia.org/wiki/American wire gauge
1
