Exam 28: Magnetic Fields

A loop of current-carrying wire has a magnetic dipole moment of 5.0 * 10^-4 A.m². The moment initially is aligned with a 0.50-T magnetic field. To rotate the loop so its dipole moment is perpendicular to the field and hold it in that orientation, you must do work of:

The diagrams show five possible orientations of a magnetic dipole in a uniform magnetic field . For which of these is the potential energy the greatest?

At one instant an electron (charge = -1.6 *10^-19C) is moving in the xy plane, the components of its velocity being v_x = 5.0 *10⁵ m/s and v_y = 3.0 * 10⁵ m/s. A magnetic field of 0.80 T is in the positive y direction. At that instant the magnitude of the magnetic force on the electron is:

The figure shows a uniform magnetic field directed to the left and a wire carrying a current into the page. The magnetic force acting on the wire is:

Which is NOT one of the differences between a cyclotron and a synchrotron?

An electron is launched with velocity in a uniform magnetic field . The angle $\theta$ between and is between 0 and 90^o. As a result, the electron follows a helical path. The pitch of the helix is:

The diagram shows a straight wire carrying a flow of electrons into the page. The wire is between the poles of a permanent magnet. The direction of the magnetic force exerted on the wire is:

An electron travels due north through a vacuum in a region of uniform magnetic field that is also directed due north. It will:

The diagrams show five possible orientations of a magnetic dipole in a uniform magnetic field . For which of these does the magnetic torque on the dipole have the greatest magnitude?

A uniform magnetic field is directed into the page. A charged particle, moving in the plane of the page, follows a clockwise spiral of decreasing radius as shown. A reasonable explanation is:

The magnetic dipole moment of a current-carrying loop of wire is in the positive z direction. If a uniform magnetic field is in the positive x direction the magnetic torque on the loop is:

The direction of the magnetic field in a certain region of space is determined by firing a test charge into the region with its velocity in various directions in different trials. The field direction is:

A coil of 1000 turns of wire has a radius of 12 cm and carries a counterclockwise current of 15A. If it is lying flat on the ground, and the Earth's magnetic field points due north, has a magnitude of 5.8 x 10^-5 T, and makes a downward angle of 25° with the vertical, what is the torque on the loop?

A current is clockwise around the outside edge of this page and a uniform magnetic field is directed parallel to the page, from left to right. If the magnetic force is the only force acting on the page, the page will rotate so the right edge:

The diagram shows a straight wire carrying current i in a uniform magnetic field. The magnetic force on the wire is indicated by an arrow but the magnetic field is not shown. Of the following possibilities, the direction of the magnetic field is:

An electron and a proton both each travel with equal speeds around circular orbits in the same uniform magnetic field, as shown in the diagram (not to scale). The field is into the page on the diagram. Because the electron is less massive than the proton and because the electron is negatively charged and the proton is positively charged:

Units of a magnetic field might be:

A strip 1.2 mm wide is moving at a speed of 25 cm/s through a uniform magnetic field of 5.6 T. What is the maximum Hall voltage across the strip?

A uniform magnetic field is in the positive z direction. A positively charged particle is moving in the positive x direction through the field. The net force on the particle can be made zero by applying an electric field in what direction?

The resonance condition in a cyclotron states that: