Q.

A 20 cm long metallic rod is rotated with 210 rpm about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field 0.2 T parallel to the axis exists everywhere. The emf developed between the centre and the ring is _________ mV. Take π=227.     [2023]


Ans.

(88)

Here ω=210 rpm=210×2π60 rad.s

 ω=7π rad/s. and l=0.2 m

and B=0.2 T

emf developed across rod is =12Bωl2

       12×0.2×7π×(0.2)2=88 mV