Conceptual Physics

Chapter 22 Problems

Conceptual Problems

C.1 Two scientists are locked in a bitter dispute about the charge on a particularly famous particle of dust. Maria claims it has a

charge of 2.40×10í^19 C. Richard disagrees; he thinks its charge is 3.20×10í^19 C. Which scientist should you believe? Explain.

Maria Richard

C.2 You are given an apple and an orange. The apple has a net charge of +3×10í^17 C. The orange has a net charge of

í3×10í^17 C. With only this information, can you determine which one has more total electrons? Explain.

Yes No

C.3 In a process known as beta decay, a neutron in an unstable atomic nucleus becomes a proton, in the process ejecting an

electron and an antineutrino. (a) Use conservation of charge to determine the charge of an antineutrino. (b) Sixty billion

neutrinos (mostly from the Sun) pass through every square centimeter on Earth every second. They are hardly noticeable due

to their negligible mass and weak interaction with matter. When a neutrino and an antineutrino collide, however, they

annihilate each other and produce two (electrically neutral) gamma rays traveling in opposite directions. What is the charge of

a neutrino?

(a) C

(b) C

C.4 The Sun generates most of its light through a series of nuclear reactions called the proton-proton chain. The overall process

of these nuclear reactions can be summarized as 4 1 Hĺ 2 He + 2Ȟ + 2Ȗ + 2? where Ȟ is a small neutral particle called a

neutrino, and Ȗ is a photon (a particle of light), which is also neutral. The pre-subscripts on the element symbols H (hydrogen)

and He (helium) indicate the number of protons in the nucleus of each element. What is the charge of the unknown entity

"?"?

+2e +e 0 íe í 2 e

C.5 Under typical conditions in a safe home, classify the following materials as conductors or insulators: (a) rubber, (b) iron, (c)

copper, and (d) wood.

(a) Rubber is a(n) i. conductor

ii. insulator

.

(b) Iron is a(n) i. conductor

ii. insulator

.

(c) Copper is a(n) i. conductor

ii. insulator

.

(d) Wood is a(n) i. conductor

ii. insulator

.

C.6 Vanessa has been walking around all day, and electrons that rubbed off from the carpet have caused her to acquire a net

negative charge. Explain why her hair might stand on end.

C.7 A positively charged eraser is placed near the "0 cm" end of a 10 cm metal ruler. As a result of the induced charge effect,

which end of the ruler becomes positively charged: the "0 cm" end, or the "10 cm" end?

the "0 cm" end

the "10 cm" end

C.8 You are locked in a rubber room and given a pair of rubber gloves along with a positively charged bar of gold (marked with a

"+") and two electrically neutral bars of gold. You will be released if you can produce a negatively charged bar of gold, and

you get to keep the gold. Explain how you might accomplish this.

C.9 Two unequally charged pellets are held apart at a fixed distance. The charge on one of the pellets is halved, and the charge

on the other is doubled. How this will affect the electric force one pellet exerts on the other? Explain.

i. The force will quadruple.

ii. The force will double.

iii. The force does not change.

iv. The force will be halved.

v. The force will be quartered.

(^414) Copyright 2007 Kinetic Books Co. Chapter 22 Problems