A particle of mass `9xx10^(-5) g` is kept over a large horizontal sheet of charge density `5xx10^(-5)C` `m^(-2)`. What charge should be given to the particle so that it does not fall on release ?

Answer

`3.12xx10^(-13)C`

Explanation

Here, `m = 9xx10^(-5) g = 9xx10^(-8) kg`
`sigma = 5xx10^(-5) C m^(-2), q = ?`
In equilibrium, `F = q E = mg`
`q((sigma)/(2in_(0))) = mg`
`:. q = (2in_(0) mg)/(sigma)`
`= (2xx8.85xx10^(-12)xx9xx10^(-8)xx9.8)/(5xx10^(-5))`
`q = 3.12xx10^(-13)C`