4. Figure 3 shows a conducting bar of negligible resistance being pulled to the left by an external agent which exerts a force F on the bar. The bar slides on two parallel rails of negligible resistance. The bar has a length $l = 1.20$ m, and a uniform, constant magnetic field of 2.50 T is directed into the page.
Fig. 3
R = 6.00 $\Omega$
(a.) Describe the direction of the current induced in the arrangement above. (2 pts.)
(b.) Calculate the speed at which the bar should be moved in order to produce a current of 0.500 A in the resistor. (6 pts.)