1. Electric Fields & Forces

2. The Electric Field
Charges create an electric field around them. In thunderclouds, the field can be strong enough to ionize air, causing lightning.

3. Question 1 Coulomb’s law describes
The electric field due to a point charge.
The force between two point charges.
The electric field due to a charged rod.
The electric potential of a point charge.
Answer: B

4. Question 1 Coulomb’s law describes
The electric field due to a point charge.
The force between two point charges.
The electric field due to a charged rod.
The electric potential of a point charge.

5. Question 2 The field inside a charged parallel-plate capacitor is
Zero.
Uniform.
Parallel to the plates.
Directed from the negative to the positive plate.
Answer: B

6. Question 2 The field inside a charged parallel-plate capacitor is
Zero.
Uniform.
Parallel to the plates.
Directed from the negative to the positive plate.

7. Question 3 The electric field inside a metallic conductor is Positive.
Negative.
Zero.
Answer: C

8. Question 3 The electric field inside a metallic conductor is Positive.
Negative.
Zero.

9. Question 4
Metal spheres 1 and 2 are touching. Both are initially neutral.
The charged rod is brought near.
The charged rod is then removed.
The spheres are separated.
Afterward, the charges on the sphere are:
Q1 is + and Q2 is +
Q1 is + and Q2 is –
Q1 is – and Q2 is +
Q1 is – and Q2 is –
Q1 is 0 and Q2 is 0
Answer: E 9

10. Question 4
Metal spheres 1 and 2 are touching. Both are initially neutral.
The charged rod is brought near.
The charged rod is then removed.
The spheres are separated.
Afterward, the charges on the sphere are:
Q1 is + and Q2 is +
Q1 is + and Q2 is –
Q1 is – and Q2 is +
Q1 is – and Q2 is –
Q1 is 0 and Q2 is 0 10

11. Question 5
Metal spheres 1 and 2 are touching. Both are initially neutral.
The charged rod is brought near.
The spheres are separated.
The charged rod is then removed.
Afterward, the charges on the sphere are:
Q1 is + and Q2 is +
Q1 is + and Q2 is –
Q1 is – and Q2 is +
Q1 is – and Q2 is –
Q1 is 0 and Q2 is 0
Answer: C 11

12. Question 5
Metal spheres 1 and 2 are touching. Both are initially neutral.
The charged rod is brought near.
The spheres are separated.
The charged rod is then removed.
Afterward, the charges on the sphere are:
Q1 is + and Q2 is +
Q1 is + and Q2 is –
Q1 is – and Q2 is +
Q1 is – and Q2 is –
Q1 is 0 and Q2 is 0
Net charge is obtained if contact is broken while the spheres are polarized.
This is charging by induction. 12

13. Question 6
Based on the last experiment, where two spheres were charged by induction, we can conclude that
Only the – charges move.
Only the + charges move.
Both the + and – charges move.
We can draw no conclusion about which charges move.
Answer: D 13

14. Question 6
Based on the last experiment, where two spheres were charged by induction, we can conclude that
Only the – charges move.
Only the + charges move.
Both the + and – charges move.
We can draw no conclusion about which charges move. 14

15. Question 7
Identical metal spheres are initially charged as shown. Spheres P and Q are touched together and then separated. Then spheres Q and R are touched together and separated. Afterward the charge on sphere R is:
–1 nC or less
–0.5 nC
0 nC
+0.5 nC
+1.0 nC or more
Answer: C 15

16. Question 7
Identical metal spheres are initially charged as shown. Spheres P and Q are touched together and then separated. Then spheres Q and R are touched together and separated. Afterward the charge on sphere R is:
–1 nC or less
–0.5 nC
0 nC
+0.5 nC
+1.0 nC or more 16