A light conducting rod of length can slide without friction on two long
PHYSICS · Subjective · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A light conducting rod PQ of length 0.40m can slide without friction on two long, horizontal, parallel rails that are 0.40m apart. The rails are joined at one end by a resistor of 2.0Ω, completing a rectangular circuit. The whole arrangement is placed in a uniform vertical magnetic field of magnitude 0.80T. Neglect the resistance of the rod and rails.
(a) Calculate the magnitude of the emf induced in the rod when it is pulled along the rails with a constant speed of 5.0m s−1.
(b) Determine the magnitude of the current in the circuit and state its direction.
(c) Show that the rod experiences a magnetic force and obtain the magnitude of this force.
(d) Hence find the magnitude of the external force that must be applied to keep the rod moving at the given speed.
(e) Prove that the rate at which work is done by the external force equals the electrical power dissipated in the resistor.