A rod of length L and electrical resistance R moves through a constant uniform magnetic field B with rightwards harpoon with barb upwards on top ; both the magnetic field and the direction of motion are parallel to the rod. The force that must be applied by a person to keep the rod moving with constant velocity v with rightwards arrow on top is:

0 N

Explanation:

Magnetic force for charges moving in wire is given by

F = qvB sin θ

It can also be rewritten for a current carrying wire as

F = ILB sin θ

IL = product of the length of wire and magnitude of the current vector

B = magnetic field.

θ = the angle between the direction of current flow and the magnetic field. For this question, the direction for the two are both parallel; θ = 0°

F = IL B sin 0 = 0 N

Hope this Helps!!!