Exam 29: Magnetic Fields Due to Currents

Two long straight current-carrying parallel wires cross the x axis and carry currents I and 3I in the same direction, as shown.At what value of x is the net magnetic field zero?

A 45-m long wire is coiled so that it makes a coil containing 100 circular loops, one on top of the other.If the wire carries a current of 13 A, what is the magnetic dipole moment of the coil?

In the figure, there are three wires carrying currents in the indicated directions, and an Amperian loop.The sign of the contribution of the current in each wire to the path integral in Ampere's Law is:

A long straight cylindrical shell has an inner radius R_i and an outer radius R_o.It carries a current i, uniformly distributed over its cross section.A wire is parallel to the cylinder axis, in the hollow region (r < R_i).The magnetic field is zero everywhere in the hollow region.We conclude that the wire:

The diagram shows three equally spaced wires that are perpendicular to the page.The currents are all equal, two being out of the page and one being into the page.Rank the wires according to the magnitudes of the magnetic forces on them, from least to greatest.

The magnetic field a distance 2 cm from a long straight current-carrying wire is 2 * 10^-5 T.The current in the wire is:

Lines of the magnetic field produced by a long straight wire carrying a current are:

The diagram shows three arrangements of circular loops, centered on vertical axes and carrying identical currents in the directions indicated.Rank the arrangements according to the magnitudes of the magnetic fields at the midpoints between the loops on the central axes, from least to greatest.

Four long straight wires carry equal currents into the page as shown.The magnetic force exerted on wire F is: