A glass rod is rubbed with a piece of silk. During the process the glass rod acquires a positive charge and the silk A. acquires a positive charge also. B. acquires a negative charge. C. remains neutral. D. could either be positively charged or negatively charged. It depends on how hard the rod was rubbed.
11. The correct answer is B, it acquires a negative charge.
12. A proton carries a A. positive charge. B. neutral charge. C. negative charge. D. variable charge.
12. The answer is A, a positive charge. It is equal to coulomb. The unit is named for Charles Coulomb whose law was presented in 1785.
13. Materials in which the electrons are bound very loosely to the nuclei and can move about freely within the material are referred to as A. insulators. B. semiconductors. C. conductors. D. superconductors.
13. The answer is C, conductors.
14. A negatively charged rod is brought near one end of an uncharged metal bar but does not touch it. By induction, the end of the metal bar farthest from the charged rod will be charged • A. positive. • B. negative. • C. neutral. • D. none of the above.
14. The correct answer is B, negative. The electrons in the charged rod will “act at a distance” and repel the electrons in the metal rod – so many of them will move to the other end.
15. A positive object touches a neutral electroscope, and the rod rotates about 45 degrees. Then a negative object is brought near the electroscope, but does not touch it. What happens to the angular deflection of the rod? A. It gets smaller. B. It gets larger. C. It doesn’t change. D. Cannot be determined without further information.
15. The correct answer is A, the angle gets smaller as some of the positive charge on the electroscope is attracted to the top, away from the pivoting “metal” rod and the fixed vertical aluminum strip.