Exam 20: Magnetism

An electron traveling toward the magnetic north with speed $400 \mathrm {~km} / \mathrm { s }$ enters a region where the earth's magnetic field has the magnitude $5.0 \times 10 ^ { - 5 } \mathrm {~T}$ and is directed downward at $45 ^ { \circ }$ below horizontal. What magnitude magnetic force acts on the electron? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

A proton is projected with a velocity of 7.0 km/s into a magnetic field of 0.60 T perpendicular to the motion of the proton. What is the magnitude of the magnetic force that acts on the proton? (e = $1.60 \times 10 ^ { - 19 } \mathrm { C }$ )

A thin copper rod 1.0 m long has a mass of 0.050 kg and is in a magnetic field of 0.10 T. What minimum current in the rod is needed in order for the magnetic force to balance the weight of the Rod?

The magnetic field at a distance of $2 \mathrm {~cm}$ from a long straight current-carrying wire is $4 \mu \mathrm { T }$ . What is the magnetic field at a distance of $1 \mathrm {~cm}$ from this wire?

An electron moves with a speed of $3.0 \times 104 \mathrm {~m} / \mathrm { s }$ perpendicular to a uniform magnetic field of $0.40$ T. What is the magnitude of the magnetic force on the electron? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

A wire in the shape of an "M" lies in the plane of the paper. It carries a current of $2.0 \mathrm {~A}$ , flowing from $A$ to $E$ , as shown in the figure. It is placed in a uniform magnetic field of $0.85 \mathrm {~T}$ in the same plane, directed as shown on the right side of the figure. The figure indicates the dimensions of the wire. Note that $A B$ is parallel to $D E$ and to the baseline from which the magnetic field direction is measured. What are the magnitude and direction of the force acting on section DE of this wire?

If a calculated quantity has units of $\frac { \mathrm { N } } { \mathrm { A } \cdot \mathrm { m } }$ , that quantity could be

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 wire lying in the plane of this page carries a current directly toward the top of the page. What is the direction of the magnetic force this current produces on an electron that is moving Perpendicular to the page and outward from it on the left side of the wire?

A geophysicist measures the magnetic force on a proton that is moving vertically downward at a point $1.996 \mathrm {~km} / \mathrm { s }$ at the earth's equator. At that Iocation, the earth's magnetic magnetic field is horizontal and has a strength of $0.40 \times 10 ^ { - 4 } \mathrm {~T}$ . What are the magnitude and direction of the force she will measure? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

Two long parallel wires separated by $7.5 \mathrm {~cm}$ each carry $3.3 \mathrm {~A}$ in opposite directions. $\left( \mu _ { 0 } = \right.$ $4 \pi \times 10 ^ { - 7 } \mathrm {~T} \cdot \mathrm { m } / \mathrm { A }$ ) (a) What magnetic force per length acts on each of the wires? Is it attractive or repulsive? (b) Find the magnitude of the magnetic field midway between the two wires.

A straight $1.0 - \mathrm { m }$ long wire is carrying a current. The wire is placed perpendicular to a magnetic field of strength $0.20 \mathrm {~T}$ . If the wire experiences a force of $0.60 \mathrm {~N}$ , what is the current in the wire?

Three long parallel wires each carry 2.0-A currents in the same direction. The wires are oriented vertically, and they pass through three of the corners of a horizontal square of side $4.0 \mathrm {~cm}$ . What is the magnitude of the magnetic field at the fourth (unoccupied) corner of the square due to these wires? $\left( \mu _ { 0 } = 4 \pi \times 10 ^ { - 7 } \mathrm {~T} \cdot \mathrm { m } / \mathrm { A } \right)$

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

Two long parallel wires placed side-by-side on a horizontal table carry identical current straight toward you. From your point of view, the magnetic field at a point exactly between the two wires

A charged particle that is moving in a static uniform magnetic field

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?

A flat circular loop of wire is in a uniform magnetic field of $0.30 \mathrm {~T}$ . The diameter of the loop is $1.0$ $\mathrm { m }$ , and a 2.0-A current flows in it. What is the magnitude of the magnetic torque on the loop when the plane of the loop is parallel to the magnetic field?

An electron moving along the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, then the magnetic field must have a component

A proton, moving west, enters a magnetic field. Because of this magnetic field the proton curves upward. We may conclude that the magnetic field must have a component