Question 1
5 points
In the arrangement shown, a conducting bar of negligible resistance slides along horizontal, parallel, frictionless conducting rails connected as shown to a 1.8-Ohms resistor. A uniform 1.5-T magnetic field is perpendicular to the plane of the paper. If $L = 60$ cm, at what rate is thermal energy being generated in the resistor at the instant the speed of the bar is equal to 4.2 m/s?
8.6 W
7.8 W
7.1 W
9.3 W
1.8 W