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Fig 27-CO, p.831
Chapter 27: Current and Resistance
27.1 Electric Current
CT1: Which current is highest?
CT2: Which current is lowest?
CT3: Is current
A. a vector
B. a scalar
C. neither
P27.9 (p.769)
Chapter 27: Current and Resistance
27.2 Resistance
R = V/I in Ohms ()
CT4: Suppose a current carrying ohmic metal wire has a cross-sectional area that gradually becomes smaller from one end to the other. Conservation of charge dictates that the current must have the same value throughout the wire. As the area of the wire becomes smaller the
A. drift velocity decreases and resistance per
length increases.
B. drift velocity and resistance per length both
decrease.
C. drift velocity and resistance per length both
increase.
D. drift velocity increases and resistance per
length decreases.
CT5: A cylindrical wire has a radius r and length l. If both r and l are doubled, the resistance will
A. remain the same.
B. double.
C. quadruple.
D. halve.
E. quarter.
l
r
R = V/I
R = l/A
P27.11 (p.769)
Histrogram for PHYS202 Exam 1 Spring 2008Average = 50 Low = 20 High = 75
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Histrogram for PHYS202 Total 1 Spring 2008Average = 55 Low = 16 High = 76
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Fig 27-7b, p.838
= 0[1+(T – T0)]
R = R0[1+(T – T0)]
0 and R0 are at T0
T = temperature
= temperature coefficient of resistance
P27.20 (p.770)
Chapter 27: Current and Resistance
27.4 Resistance and Temperature
Fig 27-11, p.844
Fig 27-10, p.844
Fig 27-12, p.844
CT6: The current at c is
A. greater than that at d.
B. less than that at d.
C. equal to that at d.
Imagine bringing dq through any circuit element in time dt
dU = dqV
Power = P = dU/dt = (dq/dt)V
P = IV
P27.26 (p.770)
Chapter 27: Current and Resistance
27.6 Electrical Power
CT7: The rank order in current from greatest to least is
A. ace.
B. aec.
C. cea.
D. cae.
E. eca.
F. eac.
