SAT Physics Practice Test: Electric Forces and Fields

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Question 10 questions

Time 8 minutes

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1. If the distance between two positive point charges is tripled, then the strength of the electrostatic repulsion between them will decrease by a factor of

A. 3
B. 6
C. 8
D. 9
E. 12

2. Two 1 kg spheres each carry a charge of magnitude 1 C. How does FE, the strength of the electric force between the spheres, compare with FG, the strength of their gravitational attraction?

A. FE < FG
B. FE = FG
C. FE > FG
D. If the charges on the spheres are of the same sign, then FE > FG ; but if the charges on the spheres are of opposite sign, then FE < FG.
E. Cannot be determined without knowing the distance between the spheres

3. The figure below shows three point charges, all positive. If the net electric force on the center charge is zero, what is the value of ?

A.
B.
C.
D.
E.

4.

The figure above shows two point charges, +Q and –Q. If the negative charge were absent, the electric field at point P due to +Q would have strength E. With –Q in place, what is the strength of the total electric field at P, which lies at the midpoint of the line segment joining the charges?

A. 0
B.
C.
D. E
E. 2E

5. A sphere of charge +Q is fixed in position. A smaller sphere of charge +q is placed near the larger sphere and released from rest. The small sphere will move away from the large sphere with

A. decreasing velocity and decreasing acceleration.
B. decreasing velocity and increasing acceleration.
C. decreasing velocity and constant acceleration.
D. increasing velocity and decreasing acceleration.
E. increasing velocity and increasing acceleration.

6. An object of charge +q feels an electric force FE when placed at a particular location in an electric field, E. Therefore, if an object of charge –2q were placed at the same location where the first charge was, it would feel an electric force of

A.
B. –2FE
C. –2qFE
D.
E.

7. A charge of –3Q is transferred to a solid metal sphere of radius r. Where will this excess charge reside?

A. –Q at the center, and –2Q on the outer surface
B. –2Q at the center, and –Q on the outer surface
C. –3Q at the center
D. –3Q on the outer surface
E. –Q at the center, –Q in a ring of radius r, and –Q on the outer surface

8. Which of the following statements is true?

A. Electric field vectors point toward a positive source charge, and the resulting electric force on an electron would point in the same direction as the electric field vector.
B. Electric field vectors point toward a positive source charge, and the resulting electric force on an electron would point in the opposite direction from the electric field vector.
C. Electric field vectors point toward a negative source charge, and the resulting electric force on an electron would point in the same direction as the electric field vector.
D. Electric field vectors point toward a negative source charge, and the resulting electric force on an electron would point in the opposite direction from the electric field vector.
E. None of the above

9.

The figure above shows two point charges, +Q and +Q. If the right-hand charge were absent, the electric field at Point P due to +Q would have a strength of E. With the right-hand charge in place, what is the strength of the total electric field at P, which lies at the midpoint of the line segment joining the charges?

A. 0
B.
C.
D. 2E
E. 4E

10.

The figure above shows four point charges fixed in position at the corners of a square. What charge would have to be present at the bottom right location for the electric field at the center of the square to be zero?

A. +Q
B. +Q
C. +2Q
D. +3Q
E. +4Q