A vertical disc of diameter 10 cm makes 20 revolutions per second about a horizontal axis passing through its centre. A uniform magnetic field `10^(-1)` T acts perpendicular to the plane of the disc. Calculate the potential difference between its centre and rim in volts.

Explanation

As we know, disc is equivalent to a rod of length r. Divide disc into rods, each rod can be replaced by a battery and these batteries are would be parallel in arrangement.

According to the question, radius of disc,
`r=(10)/(2)=5cm=0.05m`
Angular velocity, `omega=20xx2pi=40pi"rad/s"`
Magnetic field, `B=10^(-1)T`
The emf of a disc is given as
`e=(1)/(2)Bomegar^(2)=(1)/(2)(10^(-1))(40pi)(0.05)^(2)`
`rArr" "V_(O)-V_(A)=1.57xx10^(-2)V`