Exam 24: Magnetic Fields and Forces

Alpha particles, each having a charge of +2e and a mass of 6.64 ×10^-27 kg, are accelerated in a uniform 0.80-T magnetic field to a final orbit radius of 0.30 m. The field is perpendicular to the velocity of the particles. How long does it take an alpha particle to make one complete circle in the final orbit? (e = 1.60 × 10^-19C)

A wire carrying a current is shaped in the form of a circular loop of radius 4.0 mm. If the magnetic field strength at its center is $1.1 \mathrm { mT }$ with no external magnetic fields present, what is the magnitude of the current flowing through the wire? (μ₀ = 4π × 10^-7 T ∙ m/A)

Two long parallel wires are placed side-by-side on a horizontal table and carry current in the same direction. The current in one wire is 20 A, and the current in the other wire is 5 A. If the magnetic force on the 20-A wire has magnitude F, what is the magnitude of the magnetic force on the 5-A wire? No external magnetic fields are present.

A ring with a clockwise current (as viewed from above the ring) is situated with its center directly above another ring, which has a counter-clockwise current, as shown in the figure. In what direction is the net magnetic force exerted on the top ring due to the bottom ring?

A wire in the shape of an "M" lies in the plane of the paper. It carries a current of 2.0 A, flowing from A to E, as shown in the figure. It is placed in a uniform magnetic field of 0.75 T in the same plane, directed as shown on the right side of the figure. The figure indicates the dimensions of the wire. Note that AB is parallel to DE and to the baseline from which the magnetic field direction is measured. What are the magnitude and direction of the force acting on section AB of this wire?

A circular metal loop of radius 10 cm and three long straight wires carry currents of $I _ { 1 } = 60 \mathrm {~A}$ $\mathrm { I } _ { 2 } = 20 \mathrm {~A}$ $I _ { 3 } = 70 \mathrm {~A}$ and $I _ { 4 } = 30 \mathrm {~A}$ as shown in the figure. Each of the straight wires is 20 cm from the center of the loop. The axes are shown in the figure, with the +z-axis coming out of the paper. What is the z component of the resultant magnetic field at the center of the loop? (μ₀ = 4π × 10^-7 T ∙ m/A)

After landing on an unexplored Klingon planet, Spock tests for the direction of the magnetic field by firing a beam of electrons in various directions and by recording the following observations: Electrons moving upward feel a magnetic force in the northwest direction. Electrons moving horizontally toward the north are pushed downward. Electrons moving horizontally toward the southeast are pushed upward. Mr.Spock therefore concludes that the magnetic field at this landing site is in which direction?

A very long thin wire produces a magnetic field of $0.0020 \times 10^{ - 4} \mathrm {~T}$ at a distance of $1.0 \mathrm {~mm}$ from the wire. What is the magnitude of the current? (μ₀ = 4π × 10^-7 T ∙ m/A)

The magnitude of the magnetic field that a long and extremely thin current-carrying wire produces at a distance of 3.0 µm from the center of the wire is 2.0 × 10^-3 T. How much current is flowing through the wire? (μ₀ = 4π × 10^-7 T ∙ m/A)

A proton travels at a speed of 5.0 × 10⁷ m/s through a 1.0-T magnetic field. What is the magnitude of the magnetic force on the proton if the angle between the proton's velocity and the magnetic field vector is 30°? (e = 1.60 × 10^-19C)

An ideal solenoid is wound with 470 turns on a wooden form that is 4.0 cm in diameter and 50 cm long. The windings carry a current in the sense shown in the figure. The current produces a magnetic field of magnitude $4.1 \mathrm { mT }$ at the center of the solenoid. What is the current I in the solenoid windings? (μ₀ = 4π × 10^-7 T ∙ m/A)

A long, straight, horizontal wire carries current toward the east. A proton moves toward the east alongside and just south of the wire. What is the direction of the magnetic force on the proton?

Which one of the following statements is correct?

An electron is moving to the right, as shown in the figure. Suddenly it encounters uniform magnetic field pointing out of the page. Which one of the three paths shown will it follow in the field?

Three very long, straight, parallel wires each carry currents of 4.0 A, directed out of the page as shown in the figure. These wires pass through the vertices of a right isosceles triangle as shown. Assume that all the quantities shown in the figure are accurate to two significant figures. What is the magnitude of the magnetic field at point P at the midpoint of the hypotenuse of the triangle? (μ₀ = 4π × 10^-7 T ∙ m/A)

A negatively charged particle -Q is moving to the right, directly above a wire having a current I flowing to the right, as shown in the figure. In what direction is the magnetic force exerted on the particle due to the current?

An electron, moving south, enters a magnetic field. Because of this field, the electron curves upward. We may conclude that the magnetic field must have a component

A charged particle moves with a constant speed through a region where a uniform magnetic field is present. If the magnetic field points straight upward, the magnetic force acting on this particle will be strongest when the particle moves

An object is hung using a metal spring. If now a current is passed through the spring, what will happen to this system?

Three particles travel through a region of space where the magnetic field is out of the page, as shown in the figure. What are the signs of the charges of these three particles?