A long wire lies in a tangle on the surface of a table, as shown below. When a current is run through the wire as shown, the largest component of the magnetic field at X points
A) into the table.
B) out of the table.
C) parallel to the nearest segment of wire.
D) antiparallel to the nearest segment of wire.
E) along a circle which has its center at the center of the overall loop.

Question

A long wire lies in a tangle on the surface of a table, as shown below. When a current is run through the wire as shown, the largest component of the magnetic field at X points 
A) into the table. 
B) out of the table. 
C) parallel to the nearest segment of wire. 
D) antiparallel to the nearest segment of wire. 
E) along a circle which has its center at the center of the overall loop.

Quizplus · Accepted Answer

The direction of the magnetic field can be found by using the Right-Hand Rule: If the thumb of your right hand points in the direction of the current, then the fingers curl in the direction of the magnetic field. At point X, the current is flowing out of the table (towards the reader), so the magnetic field will be in the direction that the fingers curl when the thumb points out of the table, which is up. Therefore, the largest component of the magnetic field at X points out of the table.

A Long Wire Lies in a Tangle on the Surface