Answer to Question #55904 in Electricity and Magnetism for kola

Question

17 A copper wire has resistance of
2.0Ω
at
0oC
and
2.26Ω
at
30oC
. What is its resistance at
50oC
?
2.43Ω
3.34Ω
1.52Ω
5.31Ω

18 A coil of wire has a resistance of
25.0Ω
at
20oC
and a resistance of
25.1Ω
at 35
oC
What is its temperature coefficient of of resistance?
4.5×10−4/oC
$3.5×10−3/oC
2.6×10−4/oC
4.0×10−5/oC

19 A cirrent flows in a wire of circular cross-section with the free electrons travelling with a mean drift velocity v. If an equal current flows in a wire of the same material but of twice theradius, what is the new mean drift velocity?
v/4
v/2
2v
4v

20 A wire with resistance of
8.0Ω
is drawn out through a die so that its new length is three times its original length. Find the resistance of the longer wire assuming that the resistivity and density of the material are unaffected by the drawing process.
72Ω
60Ω
80Ω
45Ω