AP Physics 2: Magnetism Full Unit

1) A wire carries a current, creating a magnetic field around itself as shown. The current in the wire is:

• A. Directed to the right

• A. Directed to the left

• A. Equal to the magnetic field

• In the same direction as the magnetic field

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

1) Two long parallel wires 40 cm apart are carrying currents of 10 A and 20 A in the opposite direction. What is the magnitude of the magnetic field halfway between the wires?

• 1.0 x 10^-5 T

• 2.0 x 10^-5 T

• 3.0 x 10^-5 T

• 4.0 x 10^-5 T

Answer explanation

The magnitude of the magnetic field halfway between the wires is determined by the formula B = (μ0 * I1 * I2) / (2 * π * d), where μ0 is the permeability of free space, I1 and I2 are the currents in the wires, and d is the distance between the wires. Plugging in the values, we get B = (4π * 10^-7 * 10 * 20) / (2 * π * 0.4) = 3.0 x 10^-5 T. Therefore, the correct choice is 3.0 x 10^-5 T.

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

1) A straight wire carries a current inside the paper. What is the direction of the magnetic field at point P?

• Points to the right

• Points to the left

• Points to the top of the page

• Points to the bottom of the page

Answer explanation

The magnetic field at point P points to the bottom of the page because a current-carrying wire produces a magnetic field that forms concentric circles around the wire.

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

Two parallel wires of length 2 m are separated by 40 cm. If the magnetic force between the two wires is 2 ×10^-6 N and the current in the second wire is twice the current in the first one.

1) Which of the following is true concerning the force between the two wires:

• The magnetic force is a repulsion between wires

• The magnetic force is an attraction between the wires

Answer explanation

The magnetic force between two parallel wires is a repulsion, as stated in the correct answer choice.

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

Two parallel wires of length 2 m are separated by 40 cm. If the magnetic force between the two wires is 2 ×10^-6 N and the current in the second wire is twice the current in the first one.

How much is the current I in the first wire?

• 1A

• 2A

• 3A

• 4A

Answer explanation

The magnetic force between two parallel wires is directly proportional to the product of their currents. Since the current in the second wire is twice the current in the first wire, the current in the first wire is 1A, which is the correct choice.

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

1) Which of the following actions would double the magnitude of the magnetic force per unit length between two parallel current-carrying wires? Choose all correct answers.

• Double one of the currents.

• Double the distance between them.

• Double both currents.

• None of the above

Answer explanation

Doubling one of the currents will double the magnitude of the magnetic force per unit length between two parallel current-carrying wires.

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

Two long, straight, parallel wires are held fixed, as shown below. A voltage is applied to wire 𝑋, creating a current 𝐼_x to the right, and the wire experiences a magnetic force of magnitude 𝐹_B toward wire 𝑌 .

which of the following statements is true.

1. It carries a current in the same direction as the current in wire 𝑋

2. It experiences a force directed away from wire 𝑋

3. It experiences a force of different magnitude than the force on wire 𝑋

• 1 only

• 2 only

• 1 and 2

• 2 and 3

Answer explanation

The wire carries a current in the same direction as the current in wire X, which causes a magnetic force towards wire Y. Therefore, statement 1 is true.

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

Which of the following is true about field lines? (Select all that apply)

• They go from a north magnetic pole to a south magnetic pole

• They go from a south magnetic pole to a north magnetic pole

• Their spacing shows the strength of the field

• They cannot cross

Answer explanation

Just like for electric fields, magnetic field lines allow us to represent the features of a magnetic field. Their spacing and direction indicate the strength and direction of the field and they start at the north magnetic pole and end at the south magnetic pole (never crossing!).

How does a magnetic field affect a moving electric charge?

• It doesn't

• It exerts a force parallel to the velocity of the charge and parallel to the direction of the field

• It exerts a force perpendicular to the velocity of the charge and parallel to the direction of the field

• It exerts a force perpendicular to the velocity and perpendicular to the direction of the field

Answer explanation

Remember your right hand rule! The velocity the charge, the direction of the field, and the force the charge experiences are all perpendicular to each other.

Tags

NGSS.HS-PS2-5

NGSS.HS-PS3-5

How does a magnetic field affect a stationary electric charge?

• It doesn't

• It exerts a force parallel to the velocity of the charge and parallel to the direction of the field

• It exerts a force perpendicular to the velocity of the charge and parallel to the direction of the field

• It exerts a force perpendicular to the velocity and perpendicular to the direction of the field

Answer explanation

A magnetic fields only exert a force on a moving electric charge.