A conducting ring of mass 2 kg and radius 0.5 m is placed on a smooth horizontal plane. The ring carries a current 4A . A horizontal magnetic field B = 10T is switched on at time t = 0 as shown in figure. The initial angular acceleration of the ring will be:

Options

A. `40pirad//s^(2)`
B. `20pi rad//s^(2)`
C. `5pi rad//s^(2)`
D. `15pi rad//s^(2)`

Answer

A

Explanation

`tau=IalphaimpliesMB=IalphaimpliesIpir^(2)B=1/2mr^(2)alpha`
`alpha=(2IBpi)/m, alpha=(2xx4xx10pi)/2=40pirad//s^(2)`