Question 1

Refer to the first image. Three long, parallel current-carrying wires are shown. The magnitudes of the currents are equal and their directions are indicated. Which of the arrows drawn near the wire carrying current $$I_1$$ correctly indicates the direction of the magnetic force acting on that wire?

Accepted Answer

C

Question 2

Refer to the second image. Three particles travel through a region of space where the magnetic field is out of the page. The electric charge of each of the three particles is, respectively:

Accepted Answer

1 is positive, 2 is neutral, and 3 is negative.

Question 3

A current-carrying loop of wire lies flat on a table top. When viewed from above, the current moves around the loop in a counterclockwise sense. For points OUTSIDE the loop, the magnetic field caused by this current:

Accepted Answer

circles the loop in a clockwise direction.

Question 4

Refer to the fourth image. The figure shows four different sets of insulated wires that cross each other at right angles without actually making electrical contact. The magnitude of the current is the same in all the wires, and the directions of current flow are as indicated. For which configuration will the magnetic field at the center of the square formed by the wires be equal to zero?

Accepted Answer

C

Question 5

A charged particle is moving in a static uniform magnetic field. Which of the following statements is true?

Accepted Answer

It may experience a magnetic force, but its speed will not change.

Question 6

A negatively-charged particle moves across a constant uniform magnetic field that is perpendicular to the velocity of the particle. The magnetic force on this particle:

Accepted Answer

causes the particle to accelerate.

Question 7

The direction of the force on a current-carrying wire in a magnetic field is:

Accepted Answer

perpendicular to both the current and the magnetic field.

Question 8

Refer to the seventh image. A long straight wire has a constant current flowing to the right. A rectangular metal loop is situated above the wire, and also has a constant current flowing through it, as shown. Which one of the following statements is true?

Accepted Answer

The net magnetic force on the rectangle is zero, but there is a nonzero torque on the rectangle.

Question 9

The magnetic force on a current-carrying wire in a magnetic field is the strongest when:

Accepted Answer

the current is perpendicular to the magnetic field lines.

Question 10

An electron moves in the plane of the page through two regions of space along the dotted-line trajectory shown in the eighth image. There is a uniform electric field in Region I directed into the plane of the page. There is no electric field in Region II. What is a necessary direction of the magnetic field in regions I and II?

Accepted Answer

Toward top of page in Region I, Out of the page in Region II

Question 11

A wire in the plane of the page carries a current directed toward the top of the page as shown. If the wire is located in a uniform magnetic field $$\vec{B}$$ directed out of the page, the force on the wire resulting from the magnetic field is:

Accepted Answer

directed to the left

Question 12

A square loop of wire carrying a current $$I is $$initially in the plane of the page and is located in a uniform magnetic field $$\vec{B}$$ that points toward the bottom of the page, as shown. Which of the following shows the correct initial rotation of the loop due to the force exerted on it by the magnetic field?

Accepted Answer

A

Question 13

Two long, straight, parallel wires in the plane of the page carry equal currents $$I in $$the same direction. Which of the following correctly describes the forces acting on the wires and the resultant magnetic field at points along the dotted line midway between the wires?

Accepted Answer

Attractive forces, not zero field

Question 14

A cross section of a long solenoid that carries current $$I is $$shown. All of the following statements about the magnetic field $$B$$ inside the solenoid are correct EXCEPT:

Accepted Answer

The magnitude of $$B is $$proportional to the distance from the axis of the solenoid.

Question 15

The three loops of wire shown in the fifteenth image are all subject to the same uniform magnetic field that does not vary with time. Loop 1 oscillates back and forth as the bob in a pendulum, loop 2 rotates about a vertical axis, and loop 3 oscillates up and down at the end of a spring. Which loop, or loops, will have an emf induced in them?

Accepted Answer

loops 2 and 3

Magnetic Forces and Fields: Step-by-Step Physics Guidance

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