大学物理: Electrostatics

Study concepts, example questions & explanations for College Physics

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Example Questions

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Example Question #4 :Gauss's Law

Gaussian surfaces A and B enclose the same positive charge +Q. The area of Gaussian surface A is three times larger than that of Gaussian surface B. The flux of electric field through Gaussian surface A is__________.

Possible Answers:

nine times larger than the flux of electric field through Gaussian surface B

three times smaller than the flux of electric field through Gaussian surface B

equal to the flux of electric field through Gaussian surface B

unrelated to the flux of electric field through Gaussian surface B

Correct answer:

equal to the flux of electric field through Gaussian surface B

Explanation:

一个ccording to Gauss's law, the total electric flux is equal to the net total electric charge inside the a Gaussian surface. If the Gaussian surface is three times larger, the electric flux will be the same if both Gaussian surfaces contain the same amount of total electric charge.

Example Question #5 :Gauss's Law

Figure 4

Which of the arrows shown in the figure represents the correct direction of the electric field between the two metal plates?

Possible Answers:

一个

C

D

B

Correct answer:

一个

Explanation:

The direction of electric field describes the trajectory of a positive test charge. Since a positive test charge would want to move away from the positive metal plate and towards the negative metal plate, the direction would be A.

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