Question

In a region with a constant magnetic field as shown, there are two conducting frictionless horizontal rails, a resistor and some conducting wire along the left side and a conducting bar on the right side that is free to slide left or right. The bar is initially at rest but at time zero a force is applied to the bar pulling it to the right so that the distance s increases with time.

X X X X X X X X x Х x Х F. Applied L R WW x x Х Х Х S

a. Magnetic flux through the loop increases as the area of the loop increases. As a result of this change in flux, a current will be induced in the loop. Use Lenz’ Law to determine the direction of the induced magnetic field inside the loop due to that induced current. Explain.

b. Explain why the induced current will be counter clock wise to create that inducted magnetic field.

c. Determine the magnetic flux through the loop when the bar is at a distance 's' to the right.

Answer 1

X L Eapplied I X X x x X Х S Ansja) the magnet field in х the region is into the page * * The flux through the loop R →E increases. According to lenz's X law the system will try 文 to oppose this increase in the magnetic flux. Hence the induced magnetic field should point out of the page. 1(b) If the induced magnetic field is pointing out of the page the using right hand sule, the current in the loop should be in counter clockwise direction. 'I' is huduced current in the figure.

LS e) let the magnetic field in the region be B. area of the ecop = A= So, the magnetic feux through the loop when the bar is at a distance s to the right =p P = 134 IRLS (the plane of the loop and magnetic field are perpendicul ar to each other.)