# 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 chargeB. the kinetic energy of a test chargeC. the potential energy of a test chargeD. the force acting on a test chargeE. the charge carried by a test charge

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

A. has zero chargeB. has charge of magnitude 1 CC. has charge of magnitude 1.6 × 10−19 CD. must be an electronE. 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 BB. greater in magnitude than the field found by BC. less in magnitude than the field found by BD. opposite in direction to the field found by BE. either greater or less than the field found by B, depending on the accelerations of the testcharges

4. The units of the electric field are:

A. N · C^{2}B. C/NC. ND. N/CE. C/m^{2}

5. The units of the electric field are:

A. J/(C·m)B. J/CC. J·CD. J/mE. none of these

6. Electric field lines:

A. are trajectories of a test chargeB. are vectors in the direction of the electric fieldC. form closed loopsD. cross each other in the region between two point chargesE. 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. 1B. 2C. 4D. 1/2E. 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 presentB. an electrical conductor is presentC. an insulator is presentD. the field points in two directions at the same placeE. the author made a mistake

9. Choose the correct statement concerning electric field lines:

A. field lines may crossB. field lines are close together where the field is largeC. field lines point away from a negatively charged particleD. a charged point particle released from rest moves along a field lineE. none of these are correct

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

A. the upper plate is positive and the lower plate is negativeB. a proton at X would experience the same force if it were placed at YC. a proton at X experiences a greater force than if it were placed at ZD. a proton at X experiences less force than if it were placed at ZE. 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/rB. kr/qC. kq/r^{3}D. kq/r^{2}E. kq2/r^{2}

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

A. Y is negative and Z is positiveB. the magnitude of the electric field is the same everywhereC. the electric field is strongest midway between Y and ZD. 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:

A. Y is negative and Z is positiveB. the magnitude of the electric field is the same everywhereC. the electric field is strongest midway between Y and ZD. Y is positive and Zis negativeE. 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/CB. 180 N/CC. 18 N/CD. 1800 N/CE. 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 particleB. 0.5 m away from the particleC. 2 m away from the particleD. 4 m away from the particleE. 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. EB. 2EC. 4ED. E/2E. E/4

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

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

18. Two point particles, with charges of q_{1} and q_{2}, 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. q_{1}and q_{2}must have the same magnitude and signB. P must be midway between the particlesC. q_{1}and q_{2}must have the same sign but may have different magnitudesD. q_{1}and q_{2}must have equal magnitudes and opposite signsE. q_{1}and q_{2}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:

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

A. ↑B. ↓C. →D. ←E. zero