Q. In the Wheatstone bridge circuit shown in Figure, R1 = 16, R2 = 8, and R3 = 40; R4 is the unknown resistance. RM is the galvanometer resistance of 6 . If no current is detected by the galvanometer, when a 24-V source with a 12- internal resistance is applied across terminals a-b, find: (a) R4, and (b) the current through R4.