Exam 30: Sources of the Magnetic Field

The figure shows a cross section of three parallel wires each carrying a current of 15 A.The currents in wires A and C are out of the paper,while that in wire B is into the paper.If the distance R = 5.0 mm,what is the magnitude of the force on a 4.0-m length of wire C?

A long cylindrical wire (radius = 2.0 cm)carries a current of 40 A that is uniformly distributed over a cross section of the wire.What is the magnitude of the magnetic field at a point which is 1.5 cm from the axis of the wire?

We find that 2N current loops are coplanar and coaxial.The first has radius a and current I.The second has radius 2a and current 2I,and the pattern is repeated up to the Nth,which has radius Na and current NI.The current in the loops alternates in direction from loop to loop as seen from above.Thus the current in the first loop is counterclockwise,in the next clockwise,up to the last loop where it is again clockwise.The magnitude of the magnetic field at the center of the loops is

Two long parallel wires lie in the xz plane. One wire passes through the point (-2 m, 0, 0) and the other through the point (+2 m, 0, 0). The wires carry equal currents in the positive z direction. 1. The magnetic field at (-3 m, 0, 0) is in the negative y direction. 2. The magnetic field at (-1 m, 0, 0) is in the positive y direction. 3. The magnetic field at (+1 m, 0, 0) is in the positive y direction. 4. The magnetic field at (+3 m, 0, 0) is in the negative y direction.

Equal currents of magnitude I travel into the page in wires M and N.Eight directions are indicated by letters A through H. The direction of the magnetic field at point P is

A thin infinitely large current sheet lies in the y-z plane.Current of magnitude J_s per unit length along the z axis travels in the y-axis direction,which is up out of the page.Which diagram below correctly represents the direction of the magnetic field on either side of the sheet?

An ideal solenoid of radius a has n turns per unit length and current I.The magnetic flux Φ_B through any area completely inside the solenoid,centered on the solenoid axis but at a 45° angle to the axis,so that it touches the inside of the solenoid,as shown below,is

What is the magnitude of the magnetic field at point P if a = R and b = 2R?

Two long parallel wires are separated by 2.0 cm.The current in one of the wires is three times the other current.If the magnitude of the force on a 2.0-m length of one of the wires is equal to 60 μN,what is the greater of the two currents?

Gauss's Law states that the net electric flux, ,through any closed surface is proportional to the charge enclosed: )The analogous formula for magnetic fields is:

One long wire carries a current of 30 A along the entire x axis.A second long wire carries a current of 40 A perpendicular to the xy plane and passes through the point (0,4,0)m.What is the magnitude of the resulting magnetic field at the point y = 2.0 m on the y axis?

A 2.0-cm length of wire centered on the origin carries a 20-A current directed in the positive y direction.Determine the magnetic field at the point x = 5.0 m on the x-axis.

Three long wires parallel to the x axis carry currents as shown.If I = 20 A,what is the magnitude of the magnetic field at the origin?

The magnetic field at (+1 m,0,0)is in the positive y direction.

Which diagram correctly shows the magnetic field lines created by a circular current loop in which current flows in the direction shown?

Two parallel and coaxial current loops of radius a are placed a distance 2L apart.The current in each ring circulates in the same direction.At a point on the axis half way between the loops the magnetic field in T has magnitude

A long straight wire (diameter = 2.0 mm)carries a current of 25 A.What is the magnitude of the magnetic field 0.50 mm from the axis of the wire?

Three coplanar parallel straight wires carry equal currents I as shown below.The current in the outer wires is directed to the right,and that in the middle wire is directed to the left.Each pair of wires is a distance a apart.The direction of the magnetic force on the middle wire

A hollow cylindrical (inner radius = 2.0 mm,outer radius = 4.0 mm)conductor carries a current of 24 A parallel to its axis.This current is uniformly distributed over a cross section of the conductor.Determine the magnitude of the magnetic field at a point that is 5.0 mm from the axis of the conductor.

When the number of turns in a solenoid and its length are both doubled,the ratio of the magnitude of the new magnetic field inside to the magnitude of the original magnetic field inside is: