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)

Fig 27-7b, p.838

 =  0 [1+(T – T 0 )] R = R 0 [1+(T – T 0 )]  0 and R 0 are at T 0 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 = dqV Power = P = dU/dt = (dq/dt)V P = IV 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.