Question

III. Two parallel cond ucting rails 25 cm apart are in a uniform 0.65 Tesla magnetic field point up out of the page (see sketch). They are resistance of 0.5 Ohms and a sliding cross bar. connected by a fixed cross bar with 12. Find the emf induced between the rails if the cross bar is pushed left, toward the fixed cross bar, at 6 m/s a) 0.825 Volts b) 2.6 Volts c) 0.975 Volts d) 0.585 Volts e) 0 Volts 13. What is the size of the current induced in the circuit by the emf? a) 1.17 Amps b) 1.95 Amps c) 0.488 Amps d) 1.65 Amps e) 0 Amps, there is no current 14. Is the flux of the magnetic field increasing, decreasing, or staying the same due to the motion of the cross bar? a) increasing since area is going down b) decreasing since area is going down c) increasing since the size of B is going up d) decreasing since the size of B is going down e) staying the same since B goes up as the area goes down, flux is conserved.

Why are the answers for 12,13,and 14 .975V, 1.95Amps, and decreasing since area is going up

Answer 1

12. Using emf = - d (B.A)/DT = Blv , here B is out of plane ,v is toward left & l is length of crossed bar   , v is consider here -be so.

emf = - .65x-.25x6 volt = .975 volts

13 . I = emf/resistance   = 0.975 volts / 0.5 ohm = 1.95 amp

14. There is induced magnetic field due to current but overall

Flux is changing due to decreasing area