Exam 20: Magnetism

A charged particle moving along the $+ x$ -axis enters a uniform magnetic field pointing along the $+ z$ -axis. A uniform electric field is also present. Due to the combined effect of both fields, the particle does not change its velocity. What is the direction of the electric field?

The maximum torque on a flat current-carrying loop occurs when the angle between the plane of the loop's area and the magnetic field vector is

Two long, parallel wires carry currents of different magnitudes. If the current in one of the wires is doubled and the current in the other wire is halved, what happens to the magnitude of the Magnetic force that each wire exerts on the other?

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?

A long straight wire carrying a 4-A current is placed along the $x$ -axis as shown in the figure. What wire? $\left( \mu _ { 0 } = 4 \pi \times 10 ^ { - 7 } \mathrm {~T} \cdot \mathrm { m } / \mathrm { A } \right)$

The figure shows a mass spectrograph that is operated with deuterons, which have a charge of $+ e$ and a mass of $3.34 \times 10 ^ { - 27 } \mathrm {~kg}$ . The deuterons emerge with negligible velocity from the source, which is grounded. The speed of the deuterons as they pass through the accelerator grid is $8.0 \times$ $10 ^ { 5 } \mathrm {~m} / \mathrm { s }$ . A uniform magnetic field of magnitude $B = 0.20 \mathrm {~T}$ , directed out of the plane, is present to the right of the grid and is perpendicular to the velocity of the deuterons. The deuterons make a circular orbit in the magnetic field. What is the radius of this orbit, and what is the initial direction of their deflection just as they enter the magnetic field? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

A flat circular wire loop lies in a horizontal plane on a table and carries current in a counterclockwise direction when viewed from above. At this point, the earth's magnetic field Points to the north and dips below the horizontal. Which side of the coil tends to lift off of the table Due to the magnetic torque on the loop?

An electron, moving west, 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 is injected into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field lines. Ignoring the particle's weight, the particle will

An ideal solenoid $20 \mathrm {~cm}$ long is wound with 5000 turns of very thin wire. What strength magnetic field is produced at the center of the solenoid when a current of $10 \mathrm {~A}$ flows through it? $\left( \mu _ { 0 } = 4 \pi \times \right.$ $\left. 10 ^ { - 7 } \mathrm {~T} \cdot \mathrm { m } / \mathrm { A } \right)$

An electron moving perpendicular to a uniform magnetic field of $0.22 \mathrm {~T}$ moves in a circle with a speed of $1.5 \times 10 ^ { 7 } \mathrm {~m} / \mathrm { s }$ . What is the radius of the circle? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } , m _ { \text {electron } } = 9.11 \times \right.$ 10-31 $\mathrm { kg }$ )

A beam of electrons is accelerated through a potential difference of $1.0 \mathrm { kV }$ before entering a velocity selector. If the magnetic field of the velocity selector has a magnitude of $0.010 \mathrm {~T}$ , what magnitude of the electric field is required if the electrons are not to be deflected as they pass through the velocity selector? $\left( \left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } , m _ { \mathrm { e } } \right. \right.$ lectron $\left. = 9.11 \times 10 ^ { - 31 } \mathrm {~kg} \right)$

A wire lying in the plane of the page carries a current toward the bottom of the page, as shown in the figure. What is the direction of the magnetic force it produces on an electron that is moving to the left directly toward the wire, as shown?

For the horseshoe magnet shown in the figure, the left end is a north magnetic pole and the right end is a south magnetic pole. When the switch is closed in the circuit, which way will the wire between the poles of the horseshoe magnet initially deflect?

Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right carries current directly toward you, and the wire on Your left carries current directly away from you. From your point of view, the magnetic field at a Point exactly midway between the two wires

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

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

Which one of the following statements is correct?

An electron moves with a speed of $8.0 \times 10 ^ { 6 } \mathrm {~m} / \mathrm { s }$ along the $+ x$ -axis. It enters a region where there is a magnetic field of $2.5 \mathrm {~T}$ , directed at an angle of $60 ^ { \circ }$ to the $+ x$ -axis and lying in the $x y$ -plane. Calculate the magnitude of the magnetic force on the electron. $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

Three very long, straight, parallel wires each carry currents of $4.0 \mathrm {~A}$ , 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? ( $\left. \mu _ { 0 } = 4 \pi \times 10 ^ { - 7 } \mathrm {~T} \cdot \mathrm { m } / \mathrm { A } \right)$