# MCAT Physics Practice Test 5: Electrostatics and Magnetism

### Test Information

15 questions

minutes

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1. Question below refers to the figure below, in which F represents the electrostatic force exerted on charged particle S by charged particle R.

In the figure, the magnitude of the electric force on R due to S is:

• A.
• B. F.
• C. 2F.
• D. 4F.

2. Question below refers to the figure below, in which F represents the electrostatic force exerted on charged particle S by charged particle R.

If the distance between the centers of the spheres is halved, the magnitude of the force on S due to R will be:

• A.
• B.
• C. 2F.
• D. 4F.

3. Question below refers to the figure below, in which F represents the electrostatic force exerted on charged particle S by charged particle R.

Assume the direction of F is the same direction as the electric field between R and S. If an electron were placed midway between R and S, the resultant electric force on the electron would be:

• A. toward R.
• B. toward S.
• C. upward in the plane of the page.
• D. downward in the plane of the page.

4. If the electric field at a distance r away from charge Q is what is the ratio of the electric fields at r, 2r, and 3r?

• A. 9:03:01
• B. 36:09:04
• C. 36:18:09
• D. 36:18:12

5. A positive charge of +Q is fixed at point R a distance d away from another positive charge of +2Q fixed at point S. Point A is located midway between the charges, and point B is a distance from +2Q, as shown below. In which direction will a positive charge move if placed at point A and point B, respectively?

• A. Toward the +Q charge for both
• B. Toward the +2Q charge for both
• C. Toward the +Q charge at point A, and toward the right at point B
• D. Toward the +2Q charge at point A, and toward the right at point B

6. Two parallel conducting plates are separated by a distance d. One plate carries a charge +Q and the other carries a charge -Q. The voltage between the plates is 12 V. If a +2 μC charge is released from rest at the positive plate, how much kinetic energy does it have when it reaches the negative plate?

• A. 2.4 × 10–6 J
• B. 4.8 × 10–6 J
• C. 2.4 × 10–5 J
• D. 4.8 × 10–5 J

7. The negative charge in the figure below (-1 μC) moves from y = -5 to y = +5 and is made to follow the dashed line. What is the work required to move the negative charge along this dashed line?

• A. –10 J
• B. -5 J
• C. 0 J
• D. 10 J

8. If the magnetic field a distance r away from a current-carrying wire is 10 T, what will be the net magnetic field at r if another wire is placed a distance 2r from the original wire and has a current twice as strong flowing in the opposite direction?

• A. 0 T
• B. 15 T
• C. 20 T
• D. 30 T

9. Given an electric dipole, the electrical potential is zero:

• A. only at the midpoint of the dipole axis.
• B. anywhere on any perpendicular bisector of the dipole axis and at infinity.
• C. anywhere on the dipole axis.
• D. only for points at infinity.

10. An electron is accelerated over a distance d by an electrical potential V. The electrical potential applied to this electron is then increased by a factor of 4 and the electron is accelerated over the same distance d. The speed of the electron at the end of the second trial will be larger than at the end of the first trial by a factor of:

• A. 16
• B. 8
• C. 4
• D. 2

11. Which of the following accurately depicts the field lines created by a proton that is moving toward the right on this page?

• A.
• B.
• C.
• D.

12. A certain 9 V battery is used as a power source to move a 2 C charge. How much work is done by the battery?

• A. 4.5 J
• B. 9 J
• C. 18 J
• D. 36 J

13. A proton and an alpha particle (a helium nucleus) repel each other with a force of F while they are 20 nm apart. If each particle combines with three electrons, what is the magnitude of the new force between them?

• A. 9F
• B. 3F
• C. F
• D.

14. A moving negative charge placed in an external magnetic field circulates counterclockwise in the plane of the paper as shown. In which direction is the magnetic field pointing?

• A. Into the page
• B. Out of the page
• C. Toward the center of the circle
• D. Tangent to the circle

15. A dipole is placed in an electric field and is allowed to come to equilibrium. How would the dipole react if the direction of the electric field is suddenly reversed?

• A. It rotates to align with the new field.
• B. It accelerates linearly along the field lines.
• C. It experiences no rotational or linear movement.
• D. It both rotates to align with the new field and accelerates linearly along the field lines.

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