## SECTION B - Induction
1978B4. Two parallel conducting rails, separated by a distance L of 2 meters, are connected through a resistance R of 3 ohms as shown above. A uniform magnetic field with a magnitude B of 2 tesla points into the page. A conducting bar with mass m of 4 kilograms can slide without friction across the rails.
(a) Determine at what speed the bar must be moved, and in what direction, to induce a counterclockwise current I of 2 amperes as shown.
(b) Determine the magnitude and direction of the external force that must be applied to the bar to keep it moving at this velocity.
(c) Determine the rate at which heat is being produced in the resistor, and determine the mechanical power being supplied to the bar.
(d) Suppose the external force is suddenly removed from the bar. Determine the energy in joules dissipated in the resistor before the bar comes to rest.