Two long, frictionless conducting rails are fixed horizontally on a laboratory bench…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Two long, frictionless conducting rails are fixed horizontally on a laboratory bench and are separated by 0.50 m. The rails are connected at one end by a copper strip that has a total electrical resistance of 4.0 Ω for the complete circuit formed by the rails, the strip, and a conducting rod that can slide without friction along the rails.
A uniform magnetic field of magnitude 0.60 T is directed vertically downward everywhere in the region occupied by the rails. A lightweight conducting rod of negligible resistance is pulled to the right along the rails at a constant speed of 2.0 m s⁻¹.
(1) Calculate the magnitude of the electromotive force (emf) induced in the rod while it is moving.
(2) Determine the magnitude and direction (clockwise or counter-clockwise as viewed from above) of the current that flows through the circuit.
(3) Compute the magnitude and direction of the magnetic force exerted on the rod by the magnetic field while it is moving at the stated speed.
(4) Find the mechanical power that must be supplied by whatever agent is pulling the rod in order to keep its speed constant, and explain the relationship between this power and the electrical power dissipated in the resistor.