Electric Fields - Chapter No 20

Right Answers have been shown below in red color.

1. An electric field is most directly related to:

A. the momentum of a test charge
B. the kinetic energy of a test charge
C. the potential energy of a test charge
D. the force acting on a test charge
E. the charge carried by a test charge

2. As used in the definition of the electric field, a “test charge”:

A. has zero charge
B. has charge of magnitude 1 C
C. has charge of magnitude 1.6 × 10−19 C
D. must be an electron
E. none of the above

3. Experimenter A uses a test charge q0 and experimenter B uses a test charge −2q0 to measure an electric field produced by stationary charges. A finds a field that is:

A. the same in both magnitude and direction as the field found by B
B. greater in magnitude than the field found by B
C. less in magnitude than the field found by B
D. opposite in direction to the field found by B
E. either greater or less than the field found by B, depending on the accelerations of the test
charges

4. The units of the electric field are:

A. N · C2
B. C/N
C. N
D. N/C
E. C/m2

5. The units of the electric field are:

A. J/(C·m)
B. J/C
C. J·C
D. J/m
E. none of these

6. Electric field lines:

A. are trajectories of a test charge
B. are vectors in the direction of the electric field
C. form closed loops
D. cross each other in the region between two point charges
E. are none of the above

7. Two thin spherical shells, one with radius R and the other with radius 2R, surround an isolated charged point particle. The ratio of the number of field lines through the larger sphere to the number through the smaller is:

A. 1
B. 2
C. 4
D. 1/2
E. 1/4

8. A certain physics textbook shows a region of space in which two electric field lines cross each other. We conclude that:

A. at least two point charges are present
B. an electrical conductor is present
C. an insulator is present
D. the field points in two directions at the same place
E. the author made a mistake

9. Choose the correct statement concerning electric field lines:

A. field lines may cross
B. field lines are close together where the field is large
C. field lines point away from a negatively charged particle
D. a charged point particle released from rest moves along a field line
E. none of these are correct

10. The diagram shows the electric field lines due to two charged parallel metal plates. We conclude that:

Electric Fields

A. the upper plate is positive and the lower plate is negative
B. a proton at X would experience the same force if it were placed at Y
C. a proton at X experiences a greater force than if it were placed at Z
D. a proton at X experiences less force than if it were placed at Z
E. an electron at X could have its weight balanced by the electrical force

11. Let k denote 1/4π60. The magnitude of the electric field at a distance r from an isolated point particle with charge q is:

A. kq/r
B. kr/q
C. kq/r3
D. kq/r2
E. kq2/r2

12. The diagram shows the electric field lines in a region of space containing two small charged spheres (Y and Z). Then:

Electric Fields 1

A. Y is negative and Z is positive
B. the magnitude of the electric field is the same everywhere
C. the electric field is strongest midway between Y and Z
D. the electric field is not zero anywhere (except infinitely far from the spheres)
E. Y and Z must have the same sign

13. The diagram shows the electric field lines in a region of space containing two small charged spheres (Y and Z). Then:

Electric Fields 1

A. Y is negative and Z is positive
B. the magnitude of the electric field is the same everywhere
C. the electric field is strongest midway between Y and Z
D. Y is positive and Zis negative
E. Y and Z must have the same sign

14. The electric field at a distance of 10 cm from an isolated point particle with a charge of 2×10−9 C is:

A. 1.8 N/C
B. 180 N/C
C. 18 N/C
D. 1800 N/C
E. none of these

15. An isolated charged point particle produces an electric field with magnitude E at a point 2 m away from the charge. A point at which the field magnitude is E/4 is:

A. 1 m away from the particle
B. 0.5 m away from the particle
C. 2 m away from the particle
D. 4 m away from the particle
E. 8 m away from the particle

16. An isolated charged point particle produces an electric field with magnitude E at a point 2 m  away. At a point 1 m from the particle the magnitude of the field is:

A. E
B. 2E
C. 4E
D. E/2
E. E/4

17. Two protons (p1 and p2) are on the x axis, as shown below. The directions of the electric field at points 1, 2, and 3, respectively, are:

Electric Fields 2

A. →, ←, →
B. ←, →, ←
C. ←, →, →
D. ←, ←, ←
E. ←, ←, →

18. Two point particles, with charges of q1 and q2, are placed a distance r apart. The electric field is zero at a point P between the particles on the line segment connecting them. We conclude that:

A. q1 and q2 must have the same magnitude and sign
B. P must be midway between the particles
C. q1 and q2 must have the same sign but may have different magnitudes
D. q1 and q2 must have equal magnitudes and opposite signs
E. q1 and q2 must have opposite signs and may have different magnitudes

19. The diagrams below depict four different charge distributions. The charge particles are all the same distance from the origin. The electric field at the origin:

Electric Fields 3

A. is greatest for situation 1
B. is greatest for situation 3
C. is zero for situation 4
D. is downward for situation 1
E. is downward for situation 3

20. The diagram shows a particle with positive charge Q and a particle with negative charge −Q. The electric field at point P on the perpendicular bisector of the line joining them is:

Electric Fields 4

A. ↑
B. ↓
C. →
D. ←
E. zero

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