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?

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

If R is the distance from a magnetic dipole, then the magnetic field it produces is proportional to:

A long straight cylindrical shell carries current i uniformly distributed over its cross section. The magnitude of the magnetic field is greatest:

A toroid with a square cross section carries current i. The magnetic field has its largest magnitude:

Magnetic field lines inside the solenoid shown are:

The magnitude of the magnetic field at point P, at the center of the semicircle shown, is given by:

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:

A long straight wire carrying a 3.0 A current enters a room through a window 1.5 m high and 1.0 m wide. The path integral around the window frame has the value (in T.m):

Electrons are going around a circle in a counterclockwise direction as shown. At the center of the circle they produce a magnetic field that is:

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

In Ampere's law, the direction of the integration around the path:

A wire carrying a large current i from east to west is placed over an ordinary magnetic compass. The end of the compass needle marked "N" will point:

The magnetic field outside a long straight current-carrying wire depends on the distance R from the wire axis according to:

Two long straight wires enter a room through a window. One carries a current of 3.0 A into the room while the other carries a current of 5.0 A out. The magnitude in T.m of the path integral around the window frame is:

Two long straight wires pierce the plane of the paper at vertices of an equilateral triangle as shown below. They each carry 2 A, out of the paper. The magnetic field at the third vertex (P) has magnitude (in T):

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.

A hollow cylindrical conductor (inner radius = a, outer radius = b) carries a current i uniformly spread over its cross section. Which graph below correctly gives B as a function of the distance r from the center of the cylinder?

Two long straight wires are parallel and carry current in the same direction. The currents are 8.0 and 12 A and the wires are separated by 0.40 cm. The magnetic field in tesla at a point midway between the wires is: