Fig 27-CO, p.831. Chapter 27: Current and Resistance 27.1 Electric Current

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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.

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