Solutions to Some Electrostatic Homeworks

SOLUTIONS TO SOME ELECTROSTATIC HOMEWORKS

How Do Electric Charges Behave?

1. electrons, protons…there are many others

2. electrons

3. a) repelb) repelc) no effectd) no effecte) attractf) no effect

g) attracth) attract

4. gains electrons

5. loses electrons

6. conducting: salt water, gold, silver, steel, tin, brass, copper, aluminum, (+ all metals)

insulating: glass, rubber, wood, plastic, cotton, wool, air, & many more

7. 23

8. protons and neutrons

How Do We Quantify Electric Charge?

1. a) +1.6 x 10-19 Cb) -1.6 x 10-19 Cc) 0 C

2. +/-1.6 x 10-19 C

3. no and no

4. proton, anti-electron, many more

5. electron, anti-proton, many more

6. b,c,h are impossible

7. 6.25 x 1018

8. 6.25 x 1018

9. 6.25 x 1018

10. 2

11. 5

12. 10

What Does “Conservation of Electric Charge” Mean?

1. each has +3 x 10-6 C

2. +0.2 C

3. +3 C, and +3/4 C

4. 0 C

5. -1.5 x 10-6 C

6. 0C, 0C, and “yes”

7. a) -3.2 x 10-19 Cb) +4.8 x 10-19 Cc) +3.2x 10-19 C

d) -8.0 x 10-19 Ce) +4.8x 10-19 Cf) +1.6x 10-18 C

g) -1.6x 10-17 Ch) 0 C

i) no such thing as 2.7 electrons!

How do Excess Electric Charges Distribute themselves on a Conductor?

1. 2. 3.

4. 5. 6.

7. We can infer that the rod is charged. Just from what is told we cannot infer anything about what type of charge the rod had.

8. We can infer that the rod is charged, and that it is charged oppositely to how the electroscope is charged.

9. Protons

Coulomb’s Law

1. G is analogous to k, and m (mass) is analogous to q(charge).

2. k = 8.99 x 109 N●m2/C2

3. Fe = 8.4 x 10-3N

4. Fe = 8 x 10-5N

5. a) x 2 b) x ¼c) x ½ d) x 1

6.