Suppose that the emf from a rod moving in a magnetic field was used to supply the current to illuminate a light bulb in a circuit, and the force needed to keep the rod moving is F. What happens to the force needed drive the motion of the rod if the light bulb is removed?
a. It is the same as when the bulb is in the circuit.
b. A larger force is needed to the keep the rod moving.
c. No force is needed: there is no longer a magnetic force to oppose the motion.