A copper ball of density `8.6 gcm^(-3), 1 cm` is diameter is immersed in oil of density `0.8 dcm^(-3)`. If the ball remiand suspended in oil in a uniform electric field of intensity `36000NC^(-1)` acting in upward direction, what is the charge on the ball ?

Options

A. `1.1 muC`
B. `4.2 muC`
C. `2.4 muC`
D. `3.7mu C`

Answer

a

Explanation

Apparent weight of the ball `=mg-upthrust`
`=4/3pir^(3)(rho-sigma)g=(4)/(3)pixx(0.5)^(3)xx(8.6-0.8)xx980`
`= 4,002 dyn e= 4.0024xx10^(-2)N`
Let `q` be the charge on the ball. As the ball remiand suspended,
`qE=` apparent weightl of the ball
or `q=("apparent weight")/(E)= (4.0024xx10^(-2))/(36,000)`
`1.11xx10^(-6)C`