Capacitance and Dielectrics

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HOMEWORK PROBLEMS Chapter 27: CAPACITANCE AND DIELECTRICS

Show the equations and calculations, and box your answer. Be sure to include the units.

NOTE: Any four questions from this HW will be graded, and the marks for this HW will be based on these only. (1, 2, 3, 12, 13, 18, 19, 21, 22, 29, 31, 32, 44)

1. A proton beam in an accelerator carries a current of 125 A. If the beam is incident on a target, how many protons strike the target in a period of 23.0 s?

2. A copper wire has a circular cross section with a radius of 1.25 mm. (a) If the wire carries a current of 3.70 A, find the drift speed of the electrons in this wire.

3. An aluminum wire having a cross-sectional area equal to 4.00 10–6 m2 carries a current of 5.00 A. The density of aluminum is 2.70 g/cm3. Assume each aluminum atom supplies one conduction electron per atom. Find the drift speed of the electrons in the wire.

12. A lightbulb has a resistance of 240 when operating with a potential difference of 120 V across it. What is the current in the lightbulb?

13. An electric heater carries a current of 13.5 A when operating at a voltage of 120 V. What is the resistance of the heater?

18. Aluminum and copper wires of equal length are found to have the same resistance. What is the ratio of their radii?

19. If the magnitude of the drift velocity of free electrons in a copper wire is 7.84 10–4 m/s, what is the electric field in the conductor?

21. If a certain silver wire has a resistance of 6.00 at 20.0°C, what resistance will it have at 34.0°C?

22. A certain lightbulb has a tungsten filament with a resistance of 19.0 when at 20.0°C and 140 when hot. Assume the resistivity of tungsten varies linearly with temperature even over the large temperature range involved here. Find the temperature of the hot filament.

29. A certain waffle iron is rated at 1.00 kW when connected…...

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