Two particles A and B having charges ` 8.0 xx 10 ^(-6) C` and `-2.0 xx 10(-6) C` respectively are held fixed with a. separtion of 20cm. Where should a thired charged. particle be placed so that it dose not experience a net electric force?.

Explanation

For force on the third charge particle to be zero. It should be palced near smaller charge, i.e. near, B and right of B.

For net force on C to be zero `F_(A)=F_(B)`
`(1)/(4 pi epsilon_(0))(Q_(1)q)/((l+x)^(2))(Q_(2)q)/(x^(2))`
`((l+x)/(x))^(2)=(Q_1)/(Q_2)=8/2=4`
`((l+x)/(x))= +-2 or l+x=+-2x`
Hence x= l. Thus the third charge should be placed 20 cm from negative charge.