AP Physics C Electricity : Electricity

Study concepts, example questions & explanations for AP Physics C Electricity

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Example Questions

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Example Question #31 : Electricity And Magnetism Exam

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A thin bar of length L lies in the xy plane and carries linear charge density , where  ranges from 0 to . Calculate the potential at the point  on the y-axis.

Possible Answers:

Correct answer:

Explanation:

Use the linear charge density  and length element , where each point is  from the point . The potential is therefore

Example Question #11 : Calculating Electric Potential

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A uniformly charged ring of radius  carries a total charge . Calculate the potential a distance  from the center, on the axis of the ring.

Possible Answers:

Correct answer:

Explanation:

Use the linear charge density  and length element . The distance from each point on the ring to the point on the axis is . Lastly, integrate over  from  to  to obtain

Example Question #181 : Ap Physics C

Ap physics c e m potential problems  2 6 16

A uniformly charged square frame of side length  carries a total charge . Calculate the potential at the center of the square.

You may wish to use the integral:

Possible Answers:

Correct answer:

Explanation:

Calculate the potential due to one side of the bar, and then multiply this by  to get the total potential from all four sides. Orient the bar along the x-axis such that its endpoints are at , and use the linear charge density . The potential is therefore

 

 

Example Question #1 : Understanding Charge Distributions On Objects

Consider a spherical shell with radius  and charge . What is the magnitude of the electric field at the center of this spherical shell?

Possible Answers:

Zero

Correct answer:

Zero

Explanation:

According to the shell theorem, the total electric field at the center point of a charged spherical shell is always zero. At this point, any electric field lines will result in symmetry, canceling each other out and creating a net field of zero at that point.

Example Question #1 : Interpreting Electric Charge Diagrams

A charge of unknown value is held in place far from other charges. Its electric field lines and some lines of electric equipotential (V1 and V2) are shown in the diagram.

Onecharge_negative_fieldandpotentiallines

A second point charge, known to be negative, is placed at point A in the diagram. In which direction will the second, negative charge freely move?

Possible Answers:

Toward the original charge Q

It will remain stationary

Toward point A

Toward point C

Correct answer:

Toward point C

Explanation:

The original charge Q is negative, as indicated by the direction of the electric field lines in the diagram. A negative point charge of any value placed at point A will cause both charges to feel a mutually repelling force on each other. Therefore, the second charge will be repelled by the original negative charge with a force pointing radially along a line connecting the center of Q and the point A, resulting in free movement toward C. Additionally, point B is on a line of equipotential to point A; negative point charges will move from regions of lower electric potential to higher electric potential (against the direction of the electric field lines), so point B is not a viable answer.

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