A metallic ring of mass 2 kg and radius 1 m with with a uniform metallic spoke of same mass 2 kg and length 1 m is rotated about its axis with angular velocity `"1 rev sec"^(-1)`. In a perpendicular uniform magnetic field B of magnitude 10 T as shown in the figure. If the central end of the spoke is connected to the rim of the wheel through a resistor R of magnitude `pi Omega` as shown. The resistor does not rotate, It's one end is always at the centre of the ring and another end is always in contact with the ring. A force F as shown is needed to maintain the constant angular velocity of the spoke then, F is equal to (The ring and the spoke has zero resistance)

Options

A. 10 N
B. 20 N
C. 50 N
D. None of these

Answer

C