A non-conducting ring having q uniformly distributed over its circumference is placed on a rough horizontal surface. A vertical time varying magnetic

Question

A non-conducting ring having q uniformly distributed over its circumference is placed on a rough horizontal surface. A vertical time varying magnetic

A non-conducting ring having q uniformly distributed over its circumference is placed on a rough horizontal surface. A vertical time varying magnetic field `B = 4t^(2)` is switched on at time t = 0. Mass of the ring is m and radius is R.
The ring starts rotating after 2 s, the coefficient of friction between the ring and the table is
A. `(4qmR)/(g)`
B. `(2qmR)/(g)`
C. `(8qR)/(mg)`
D. `(qR)/(2mg)`

Monjur Alahi

5 views

2025-01-04 04:42

1 Answers

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Salim Ahmed Kawsar · Accepted Answer · 2023-02-05T15:29:48+06:00

Salim Ahmed Kawsar

Correct Answer - C
As, E `l=(dphi_(B))/(dt)`
or `E(2piR)=piR^(2).(dB)/(dt)=piR^(2)(8t)`
`therefore" "E=4Rt`
`F=qE=4qRt" [tangential]"`
`tau_(F)=4qR^(2)t`
`tau_(f)=(mumgR)`
When `tau_(F)gt tau_(f)`, ring will start rotating.
At t = 2 s,
`8qR^(3)=mumgR`
`therefore` Coefficient of friction, `mu=(8qR)/(mg)`

5 views Answered 2023-02-05 15:29