The figure shows three long,parallel current-carrying wires.The magnitudes of the currents are equal and their directions are indicated in the figure.Which of the arrows drawn near the wire carrying current 1 correctly indicates the direction of the magnetic force acting on that wire?
A) A
B) B
C) C
D) D
E) The magnetic force on current 1 is equal to zero.

Question

The figure shows three long,parallel current-carrying wires.The magnitudes of the currents are equal and their directions are indicated in the figure.Which of the arrows drawn near the wire carrying current 1 correctly indicates the direction of the magnetic force acting on that wire? 
A) A 
B) B 
C) C 
D) D 
E) The magnetic force on current 1 is equal to zero.

Quizplus · Accepted Answer

According to the right-hand rule for magnetic forces, when the direction of the current in the wire and the direction of the magnetic field created by the other two wires is known, the direction of the magnetic force on the wire carrying the current can be determined by pointing the right thumb in the direction of the current, and the fingers of the right hand in the direction of the magnetic field. In this case, if we point the right thumb in the direction of the current in wire 1, and curl the fingers of the right hand in the direction of the magnetic field created by the other two wires, the direction of the magnetic force on wire 1 is upward, as shown by arrow A. Therefore, the correct choice is A.

The Figure Shows Three Long,parallel Current-Carrying Wires