Calculate the electric field intensity E which would be just sufficient to balance the wight of an electron. If this electric field is produced by a second electron located below the first one what would be the distance between them? [Given: `e=1.6xx10^(-19)C, m=9.1xx10^(-31)kg` and `g=9.8 m//s^(2)`]

Explanation

As force on a charge e in an electric field E
`F_(e)=eE`
So according to given problem
`F_(e)=W rArr eE=mg`
`rArr E=(mg)/(e)=(9.1xx10^(-31)xx9.8)/(1.6xx10^(-19))=5.57xx10^(-11) V/m`

As this intensity E is produced by another electron B, located at a distance r below A.
`E=(1)/(4piepsilon_(0))e/r^(2)rArr r=sqrt(e/(4piepsilon_(0)E))` So, `r=[(9xx10^(9)xx1.6xx10^(-19))/(5.57xx10^(-11))]cong 5m`