Self-Test: Electrostatics Test #1
Suggested Time: 75 minutes

1. A cathode ray tube beam deflects to the location as shown in Diagram I when a certain voltage is applied to the deflecting plates. The connections to the deflecting plates are then reversed and the deflecting voltage is reduced. Which location in Diagram II best represents the new beam position?

 A. Location 1 B. Location 2 C. Location 3 D. Location 4

2. The diagram shows the electric field lines near two point charges, L and R. Identify the polarity of these point charges. POLARITY OF L POLARITY OF R A. Negative Negative B. Negative Positive C. Positive Negative D. Positive Positive

3. Three positive charges, are fixed as shown in the diagram below. Calculate the net electric force on Q 2 due to Q 1 and Q 3 .

 MAGNITUDE OF FORCE DIRECTION OF FORCE A. 3.11 N Left B. 3.11 N Right C. 5.9 N Left D. 5.9 N Right

4. An electron orbits a nucleus which carries a charge of +9. 6 × 10 -19 C. If the electron's orbital radius is 2.0 × 10-10 m, what is its electric potential energy?
 A. -6.9 × 10 -18 J B. -3.5 × 10 -8 J C. 43 J D. 2.2 × 10 11 J

5. What is the magnitude of the electric field at point P due to the two charges positioned as shown in the diagram below? A. 5.6 × 10 4 N/C B. 8.4 × 10 4 N/C C. 2.4 × 10 5 N/C D. 8.2 × 10 5 N/C

6. What is the change in kinetic energy of an electron that moves from the negative plate to the positive plate in the situation shown below? A. A gain of 4.8 × 10 -17 J B. A loss of 4.8 × 10 -17 J C. A gain of 9.6 × 10 -16 J D. A loss of 9.6 × 10 -16 J

7. Two 2.0 × 10 -6 C charges are positioned as shown in the diagram below. What work must be done to move a 1.2 × 10 -7 C charge from location X to location Y?

 A. 3.6 × 10 -3 J B. 1.5 × 10 -2 J. C. 1.8 × 10 -2 J D. 3.9 × 10 -2 J

8. How much work is needed to move a -2.0 × 10 -6 C charge from position S to position T as shown below? A. 4.3 × 10 -2 J B. 4.8 × 10 -2 J C. 9.1 × 10 -2 J D. 1.1 × 10 -1 J

9. What is the acceleration of a proton in a uniform 2.5 × 10 5 N/C electric field as shown below? MAGNITUDE OF ACCELERATION DIRECTION OF ACCELERATION A. 2.4 × 10 13 m/s2 Right B. 2.4 × 10 13 m/s2 Left C. 1.5× 10 32 m/s2 Right D. 1.5× 10 32 m/s2 Left

10. A 6.0 × 10 6 C charge is located 4.0 m from a 3.0 × 10 6 C charge. What is the electric potential at P, halfway between the charges?

 A. -4.1 × 10 2 V B. 6.8 × 10 3 V C. 1.4 × 10 4 V D. 4.1 × 10 4 V

11. When a charge is accelerated through a potential difference of 500 V, its kinetic energy increases from 2.0 × 10 -5 J to 6.0 × 10 -5 J . What is the magnitude of the charge?

 A. 4.0 × 10 -8 C B. 8.0 × 10 -8 C C. 1.2 × 10 -7 C D. 1.6 × 10 -7 C

12. Two parallel plates 4.0 × 10 -2 m apart have a potential difference of 1000 V. An electron is released from the negative plate at the same instant that a proton is released from the positive plate. Which of the following best compares their speed and kinetic energy as they strike the opposite plate?
 SPEED OF  ELECTRON AND PROTON KINETIC ENERGY  ELECTRON AND PROTON A. Same Same B. Same Different C. Different Same D. Different Different

13. Two long, parallel plates are separated by 0.028 m and have a potential difference between them of 80 V, as shown below. Point P is located midway between the plates. What is the potential difference between point P and one of the plates?

 A. 0 V B. 40 V C. 80 V D. 160 V

14. An electron is positioned in an electric field. The force on the electron due to the electric field is equal to the force of gravity on the electron. What is the magnitude of this electric field?

A. 8.93 × 10 -30 N/C

B. 5.69 × 10 -12 N/C

C. 5.58 × 10 -11 N/C

D. 1.44 × 10 -9 N/C

15. An object with a charge of + 4.0 × 10 -18 C and a mass of 1.1 × 10 -15 kg is held stationary by balanced gravitational and electric forces midway between horizontal charged plates as shown. What is the applied voltage V A. 16 V B. 32 V C. 65 V D. 2.7 × 10 2 V

16. The diagram below shows two equally charged objects in equilibrium. The charge on the left has a mass of 3.5 g, and is suspended by a thread making an angle of 37o the vertical. The charges have separation distance of 9.6 cm. What is the magnitude of the charge on each object? (7 marks) 17. A 2.5 × 10 -7 C charge is initially located 7.0 m from a fixed 8.0 × 10 -6 C charge. a) What is the minimum amount of work required to move the 2.5 × 10 -7 C charge 2.0 m closer as shown? (5 marks)

b) If the 2.5 × 10 -7 C charge is moved a further 2.0 m closer to the 8.0 × 10 -6 C charge, will the additional work required be, less than, the same, or greater than the work required in (a)? (2 marks)

18. Two point charges Q 1 and Q 2 are arranged as shown in the diagram below. The electric potential at point P due to these charges is found to be 1.9 × 10 5 V. What are the magnitude and sign of charge Q 1? (7 marks)

19. An electron moving at 7.5 × 10 6 m/s enters an electric field between parallel plates by passing through a small hole in one of the plates. What is the impact speed of the electron on the second plate? (7 marks)

20. Two charges are positioned as shown in the diagram below. a) Find the magnitude and direction of the electric field at A. (4 marks)

b) A charge placed at A experiences a force of 4.0 × 10 -3 N towards the right. What are the magnitude and polarity of this charge? (3 marks)

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