Chapter 9

Exercises

3. The loss of electrons produces a positive charge, thus your hair will be positively charged and the comb negatively charged.

7. Half their original separation yields 4 times the original force, one quarter their original separation yields 16 times the force. Moved 4 times further and the result will be 1/16 the original force.

9. 10 joules per coulomb is 10 volts (p. 208). When released, its 10 joules of potential energy, this becomes 10 joules of kinetic energy as is passes its starting point.

14. The cooling system of an automobile. In an electrical circuit electrons travel in a path in which they start and end at the same location. This is similar to the path water takes in the automobiles cooling system, start in the radiator and then returning their.

15. The bulb grows brighter.

18. It goes to heat. In fact, about 95% of the electrical energy fed to an incandescent lamp goes to heat.

19. Thick wires have less resistance and will more effectively carry currents without excessive heating.

22. Plugging a 110-V appliance into a 220-V source will burn up the appliance as too much current was provided. Interestingly enough, though, if a 220-V appliance with an electric motor is plugged into a 110-V power source the motor can also burn out. The motor turns too slow allowing too much current to build up in the motor coils.

24. Home - AC, car - DC.

30. Bulb C is the brightest and draws the most current, and has the most voltage applied across it. A unscrewed - B goes out, nothing happens to C. C unscrewed - A and B glow as if nothing happened.