SEATWORK 11

1. A 5.00-A current runs through a 12-gauge copper wire (diameter 2.05 mm) and through alight bulb. Copper has 8.5 x 1028free electrons per cubic meter.

(a) How many electrons pass through the light bulb each second?(b) What is the current density in the wire?(c) At what speed does a typical electron pass by any given point in the wire?(d) If you were to use wire of twice the diameter, which of the above answers would

change? Would they increase or decrease?

2. A conductor of uniform radius 1.20 em carries a current of 3.00 A produced by anelectric field of 120V/m. What is the resistivity of the material? l

3. The] 8-gauge copper wire has a diameter of 1.02 mrn and a cross-sectional area of8.20 x10-7 m2. 1t carries a current of 1.67 A. Find:

(a) the elecl ric-field magnitude in the wire(b) the potential difference between two points in the wire 50.0 m apart; and(c) the resistance ofa 50.0-m length of this wire.

4. Suppose the resistance of the wire in #3 is 1.050 at a temperature of20cC Find theresistance at O°C and at 100°e.

5. A.lightbulb has a resistance of 240 n when operating with a potential difference of 120 Vacross it. What is the current in the lightbulb?

6. A current-carrying gold wire has diameter 0.84 mm. The electric field in the wire is 0.49V1m. What are

(a) the current carried by the wire;(b) the potential difference between two points in the wire 6.4 m apart;(c) the resistance ofa 6.4-m length of this wire?

(b)

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7. Find the equivalent resistance between points a andb:

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