The speed of a point on the disk at a distance `r'` for `0lt= r' lt=r` from the axis is `v=omega r'` , so the force per unit charge is `f_(mag)=v xx B=omega r' B` radially outward. The emf is therefore,

`epsilon=int f_(mag) * dl=int_0^r omega r' B dr'=1/2 omega Br^2`

The current is then

`I=epsilon/R=(omega Br^2)/R`

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