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Fig 27-CO, p.831

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 vector a scalar neither P27.9 (p.769). Chapter 27: Current and Resistance 27.2 Resistance. R = V/I in Ohms ().

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Fig 27-CO, p.831

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  1. Fig 27-CO, p.831

  2. Chapter 27: Current and Resistance 27.1 Electric Current

  3. CT1: Which current is highest? • CT2: Which current is lowest? • CT3: Is current • a vector • a scalar • neither • P27.9 (p.769)

  4. Chapter 27: Current and Resistance 27.2 Resistance R = V/I in Ohms ()

  5. 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 • drift velocity decreases and resistance per length increases. • drift velocity and resistance per length both decrease. • drift velocity and resistance per length both increase. • drift velocity increases and resistance per length decreases.

  6. r l • CT5: A cylindrical wire has a radius r and length l. If both r and l are doubled, the resistance will • remain the same. • double. • quadruple. • halve. • quarter.

  7. R = V/I R = l/A P27.11 (p.769)

  8. Fig 27-7b, p.838

  9. Chapter 27: Current and Resistance 27.4 Resistance and Temperature  = 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)

  10. Fig 27-11, p.844

  11. Fig 27-10, p.844

  12. Fig 27-12, p.844

  13. CT6: The current at c is • greater than that at d. • less than that at d. • equal to that at d.

  14. Chapter 27: Current and Resistance 27.6 Electrical Power 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)

  15. CT7: The rank order in current from greatest to least is • ace. • aec. • cea. • cae. • eca. • eac.

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