Consider the situation shown in the figure of the previous problem. Suppose the wire connecting O and C has zero resistance but the circular loop has a resistance R uniformly distributed along its length. The rod OA is made of rotate with a uniform angular speed ω as shown in the figure. Find the current in the rod when AOC = 90°.

Given:


Resistance of circular loop = R


AOC = 90°


Angular velocity = w


Formula used:


From the previous problem, emf … (i), where B = magnetic field, w = angular velocity, a = radius


Now, since AOC = 90°, the major and minor segments of the arc AC consist of parallel combination of resistances of R/4 and 3R/4 respectively (since the resistance is divided in the ratio of the angle at the centre).


Hence, equivalent resistance =


Therefore, current through the rod , where E = emf, R’ = equivalent resistance


= (Ans)


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