Three coplanar parallel straight wires carry equal currents I to the right as shown below. The current in the upper two wires is directed to the right, but the current in the bottom 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.
Answer: C
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