A single current-carrying circular loop of radius R is placed next to a long, straight wire, as shown in the figure. The current I in the wire flows to the right. In which direction must current flow in the loop to produce a net magnetic field of zero at its center?
A) counterclockwise
B) clockwise
C) It could be either clockwise or counterclockwise.
D) The current in the loop should be zero.

Question

A single current-carrying circular loop of radius R is placed next to a long, straight wire, as shown in the figure. The current I in the wire flows to the right. In which direction must current flow in the loop to produce a net magnetic field of zero at its center? 
A) counterclockwise 
B) clockwise 
C) It could be either clockwise or counterclockwise. 
D) The current in the loop should be zero.

Quizplus · Accepted Answer

According to the Right Hand Rule, the magnetic field produced by the current in the wire at the center of the loop points out of the page, perpendicular to the plane of the loop. To cancel out this magnetic field, the current in the loop must produce a magnetic field pointing into the page. This can be achieved by using the Right Hand Rule again and determining that current must flow clockwise in the loop. Therefore, the correct answer is B) clockwise.

A Single Current-Carrying Circular Loop of Radius R Is Placed