1. In the following problem, square charged particles are fixed; round charged particles are free to move, and always start from rest..

Circle the vector that best shows the net force on the negative round particle by two fixed particles located in the positions shown below.

2. In each diagram below, draw a vector showing the net force on the round particle due to all the square fixed charges.

3. Explain briefly why repulsion is a better test for the sign of a charged object than attraction is.

4. Would you use charging by contact or charging by induction to deposit charge of the same sign as the rod? Explain, using diagrams.

5. Can you charge a piece of plastic by induction? Explain, using diagrams.

6. Metal sphere A is charged negatively and then brought near an uncharged metal sphere B. Both spheres rest on insulating supports, and the humidity is very low.

Use +'s and -'s to show the approximate distribution of charges on the two spheres. (Hint: think hard about both spheres, not just B.)

7. You have three metal blocks marked A, B, and C, sitting on insulating stands. Block A is charged "+" but blocks B and C are neutral.

Without using any additional equipment, and without altering the amount of charge on block A,

explain how you could make block B be charged "+" and block C be charged "-". Explain your

procedure in detail, including diagrams of the charge distributions at each step in the process.

8. An electron is observed to accelerate northward with an acceleration of 1.6 x 106 m / s2. (Electron mass = 9x10-31kg, charge is -e, where e = 1.6x10-19C.) Explain how to use the definition of electric field to determine the electric field at this location, and give the direction and magnitude of the field.

9. Here is a neutral, solid piece of metal placed between two point charges. On a similar sketch, indicate the polarization of the piece of metal.

Then, at location A inside the solid piece of metal, carefully draw and label these vectors: 1) the electric field due to each of the two point charges and 2) the electric field due to the surface charges on the metal. Explain briefly why you drew the vectors the way you did.

10. On a clear and carefully drawn diagram, place a zorac nucleus and a proton in such a way that the electric field due to these charges is zero at a location marked x. (A zorac nucleus contains three protons and three neutrons.) Explain briefly but carefully, and use diagrams to help in the explanation. Be quantitative about the relative distances (That means give a formula for one distance in terms of the other, or give an algebraic expression for the ratio of the two).

11. On a clear and carefully drawn diagram, place a zorac nucleus and an electron in such a way that the electric field due to these charges is zero at a location marked x. Explain briefly but carefully, and use diagrams to help in the explanation. Be quantitative about the relative distances. (That means give a formula for one distance in terms of the other, or give an algebraic expression for the ratio of the two)

You are the captain of a spaceship. You need to measure the electric field at a specified location P in space outside your ship. You send a crew member outside with a meter stick, a stopwatch, and a small ball (f known mass M and net charge +Q (held by insulating strings while being carried). You must explain to the crew member what observations of the ball to make for you, and explain how you will use those observations to determine the magnitude and direction of the electric field at location P.

12. Write down the instructions (in step by step form) you will give to the crew member.

13. Explain how you will analyze the data that the crew member brings you, to determine the magnitude and direction of the electric field at location P.

Use the figure below for problems 14 & 15. At a particular moment, one negative and two positive charges are located as shown:

14. Find the x and y components of the electric force on Q1 exerted by the other two charges.

15. What are the x and y components of the electric field at location A, directly to the right of Q1 and directly above Q3?

5 Pts Bonus. A helium nucleus (He4, containing two protons and two neutrons. also called an "alpha particle") is released from rest at location A. What are the x and y components of the initial acceleration of the helium nucleus? The mass of a He4 nucleus is practically the same as the mass of a He4 atom, (4x10-3 kg/mole)/(6x1023atoms/mole), because protons and neutrons are about 2000 times as massive as electrons.

16. One way to stick balloons onto the wall is to rub the balloon and press the rubbed part onto thewall. This is because:

(A) rubber is soft and so it will melt due to the heat produced by rubbing.

(B) rubber gets charged. This will induce opposite charges on the wall, which attracts the rubber.

(C) actually we can stick balloons if the balloon has a net positive charge or a net negative charge.

(D) Both A and B.

(E) both B and C.

17. In which case(s) will the square mass get lifted off the ground?

(A) Figure A

(B) Figure B

(C) Figure C

(D) Figure D

(E) Figures C and D

18. The force on charge q2(+) due to charge q1(+) has:

(A) + X and + Y components. (B) - X and - Y components. (C) - X and + Y components. (D) + X and - Y components.

19. Three charges q1(+), q2(+), and q3(-) are placed at the corners of an equilateral triangle as shown with q, on the left, q2 at the top corner and q3 on the right. What is the direction of the net force on the charge q2 due to q1 and q3? Assume magnitudes of the charges q~ = q2 = q3 = q coulombs.

(A) Net force is along + X. (B) Net force is along - X. (C) Net force is along + Y. (D) Net force is along - Y. (E) Net force has X and Y components.