OUTLINE OF SOLUTIONS
PHYS102
SPRING08
QUIZIII
Time Limit: 50 min.
NOTE:
For Prob.1, below, please circle the answer of your choice for each part.
1a
. Two wires each of length, L are made of the same material of electrical resistivity
ρ
and have uniform but different crosssectional areas. The ratio of their crosssectional
areas is 2:1. What is the corresponding ratio of their electrical resistance?
(a). 2:1
( b) 1:1
(c) 1:2
(d). 1:4
(Resistance is inversely proportional to the crosssectional area)
1b
. How much energy (in units of
J)
is dissipated as heat during a twominute time
interval by a 1.5
k
Ω
resistor that has a constant 20.0
V
potential difference across its
leads?
(a.) 30
(b) 46
c)
32
(d) 72
(Energy = P*
Δ
t = I
2
R
Δ
t = V
2
Δ
t/R = 400*2*60/1500 = 32J)
1c
.The diagram to the right shows part of
an electrical circuit. The current through
the 4.0
Ω
resistor is (in units of
A
) :
(a) 0.1
(b) 0.15
(c) 0.2
(d) 0.6
(i
4
+i
2
= 0.3A and 4i
4
= 2i
2
, solve these equations to get i
4
= 0.1A)
1d
. Consider an initially uncharged capacitor, C in a series RC circuit. The switch S is
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 Spring '08
 N/A
 Physics, RC circuit, Electrical resistance, Electrical network, Electrical impedance, different crosssectional areas, Assume I3

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