SAT Physics Practice Questions: Magnetism

This collection of SAT Physics subject test questions focuses on magnetism concepts, including magnetic fields, forces on moving charges, and forces on current-carrying wires. These problems are designed to be similar in style and difficulty to those found on the actual SAT Physics test.

Note: In the following questions, vector quantities are represented in boldface. We use LaTeX notation for mathematical expressions.

  1. A positively charged particle with charge \(q\) moves with velocity \(\mathbf{v}\) perpendicular to a uniform magnetic field \(\mathbf{B}\). If the magnitude of the velocity \(|\mathbf{v}|\) is doubled, what happens to the magnitude of the magnetic force \(\mathbf{F}\) acting on the particle?

    A) Halved
    B) Doubled
    C) Quadrupled
    D) Quartered
    E) Unchanged

  2. What is the direction of the force acting on a negatively charged particle moving from East to West in a magnetic field directed downward (into the page)?

    A) Directed to the north (right)
    B) Directed to the south (left)
    C) Directed upward
    D) Directed into the page
    E) Directed out of the page

  3. A negatively charged particle \(q\) enters from the left an area containing both an electric field directed downward and a magnetic field of magnitude \(6.0 \times 10^{-6} \, \text{T}\) directed into the page, as shown below. What must be the magnitude of the electric field so that the particle is not deflected if the magnitude of its velocity is \(2.0 \times 10^{5} \, \text{cm/s}\)?

    Charged particle in crossed electric and magnetic fields
    A) \(1.2 \, \text{V/m}\)
    B) \(3.3 \times 10^{-11} \, \text{V/m}\)
    C) \(1.2 \times 10^{-2} \, \text{V/m}\)
    D) \(3.3 \times 10^{10} \, \text{V/m}\)
    E) \(120 \, \text{V/m}\)

  4. Which of the following diagrams represents the directions of the forces acting on two parallel wires carrying current \(I\) in the same direction?

    Two parallel wires with currents in the same direction Force diagrams for parallel current-carrying wires

  5. If a force \(\mathbf{F}\) is exerted on a charged particle when it enters a magnetic field \(\mathbf{B}\) with velocity \(\mathbf{v}\), which of the following statements is always true?

    A) Vectors \(\mathbf{F}\), \(\mathbf{B}\), and \(\mathbf{v}\) are all perpendicular to each other
    B) Vectors \(\mathbf{F}\) and \(\mathbf{B}\) are parallel
    C) Vectors \(\mathbf{F}\) and \(\mathbf{B}\) are perpendicular
    D) Vectors \(\mathbf{F}\) and \(\mathbf{v}\) are parallel
    E) Vectors \(\mathbf{B}\) and \(\mathbf{v}\) may be perpendicular

  6. If a magnetic field \(\mathbf{B}\) exerts a force \(\mathbf{F}\) on a wire of length \(L\) carrying current \(I\), what value of the angle \(\theta\) between the direction of the current and the magnetic field gives the maximum magnitude of \(F\)?

    A) \(180^\circ\)
    B) \(45^\circ\)
    C) \(90^\circ\)
    D) \(120^\circ\)
    E) \(0^\circ\)

  7. What is the direction of the current that experiences the force \(\mathbf{F}\) in the magnetic field \(\mathbf{B}\) shown in the diagram below?

    Force on current-carrying wire in magnetic field
    A) Upward
    B) Into the page
    C) Downward
    D) From left to right
    E) From right to left

  8. In the circuit below, wire PQ is part of a closed circuit and is in a magnetic field \(\mathbf{B}\). Neglecting wire resistance and battery internal resistance, which statements are true about the magnitude of the force acting on wire PQ?

    1. It is proportional to the magnitude of \(\mathbf{B}\)
    2. It is inversely proportional to \(R\)
    3. It is inversely proportional to \(E\)
    Circuit with wire in magnetic field
    A) (I) only
    B) (I), (II), and (III)
    C) (I) and (III) only
    D) (I) and (II) only
    E) (II) and (III) only

  9. Two parallel wires with equal currents \(I\) exert forces on each other with equal magnitudes. What happens to the magnitude of this force if the current in each wire is halved?

    A) The magnitude is quartered
    B) The magnitude is halved
    C) The magnitude is doubled
    D) The magnitude is quadrupled
    E) The magnitude does not change

  10. In the circuit below, wire PQ has a mass of 10 grams and length of 20 cm, and can move up and down with negligible friction. A uniform magnetic field \(\mathbf{B}\) of magnitude 1 T is directed out of the page. What must be the direction and minimum current in the circuit to lift wire PQ upward?

    Wire in magnetic field that can move vertically
    A) Direction: from Q to P, Minimum intensity: 2 A
    B) Direction: from P to Q, Minimum intensity: 0.5 A
    C) Direction: from P to Q, Minimum intensity: 2 A
    D) Direction: from Q to P, Minimum intensity: 1 A
    E) Direction: from Q to P, Minimum intensity: 0.5 A

Detailed solutions and explanations are available at SAT Physics Magnetism Solutions.