Qwizdom questions for Jan. 15, 2010

1. Qwizdom questions for Jan. 15, 2010

2. 21. One coulomb per volt is a • joule • electron-volt C. farad D. watt

3. 21. The correct answer is C, farad. For a capacitor: C = Q/V

4. A dielectric material such as paper is placed between the plates of a capacitor. What happens to the capacitance? A. no change B. becomes larger C. becomes smaller

5. 22. The answer is B, the capacitance increases. Recall that The dielectric constant, K = 3.7 for paper.

6. Doubling the voltage across a given capacitor causes the energy stored in that capacitor to • A. quadruple • B. double • C. reduce to one half • D. reduce to one fourth

7. 23. The answer is A, the energy quadruples. So if V is doubled, U will be four times as large.

8. 24. Consider two copper wires. One has twice the cross-sectional area of the other. How do the resistances of these two wires compare? • A. Both wires have the same resistance. • The thicker wire has half the resistance of • the thinner wire. • The thicker wire has twice the resistance • of the thinner wire.

9. 24. The correct answer is B since and the thicker wire has a larger cross-sectional area.

10. 25. A kilowatt-hour is equivalent to A. 1000 W B. 3600 s C. 3,600,000 J/s D. 3.6 MJ

11. 25. The correct answer is D.

12. Done with Qwizdom