A metal conductor of length 1 m rotates in vertical plane about an axis passing through one of its ends at angular velocity 4 rad s^-1. What is the emf developed between the two ends of the conductor, if the horizontal component of the earth's magnetic field is 0.2 G ?

40 µV

$ \xi = \frac{1}{2} B\omega l^2 = \frac{1}{2} \times 0.2\times 10^{-4}\times 4\times 1^2 = 40\mu V$