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) is up out of the plane of the wires.
B) is down into the plane of the wires.
C) is in the plane of the wires, directed upwards.
D) is in the plane of the wires, directed downwards
E) cannot be defined, because there is no magnetic force on the middle wire.

Question

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) is up out of the plane of the wires. 
B) is down into the plane of the wires. 
C) is in the plane of the wires, directed upwards. 
D) is in the plane of the wires, directed downwards 
E) cannot be defined, because there is no magnetic force on the middle wire.

Quizplus · Accepted Answer

The Answer of 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) is up out of the plane of the wires. 
B) is down into the plane of the wires. 
C) is in the plane of the wires, directed upwards. 
D) is in the plane of the wires, directed downwards 
E) cannot be defined, because there is no magnetic force on the middle wire.

Three Coplanar Parallel Straight Wires Carry Equal Currents I as Shown