A 1 m long metal rod AB completes the circuit as shown in figure. The area of circuit is perpendicular to the magnetic field of 0.10 T. If the resistance of the total circuit is 2 then the force needed to move the rod towards right with constant speed (v) of 1.5 m/s is N. [figure]
- 5.7 10-2
- 7.5 10-3
- 5.7 10-3
- 7.5 10-2
Answer
(2) 7.5 10-3
Solution
Motional emf in the rod: = Bvl = 0.10 1.5 1 = 0.15 V
Current: I = R = 0.152 = 0.075 A
Magnetic force on the rod (opposes the motion): FB = BIl = 0.10 0.075 1 = 7.5 10-3 N
For constant speed, the applied force balances FB.
F = 7.5 10-3 N
Answer: (2)