Two point charges of `+1muC` and `+4muC` are placed `0.15` m apart. Find the location of null - points between them.
The point between the two charges, where net electric field due to them is zero, is called null - point.

Explanation

Given, `q_(1)=+1muC=1xx10^(-6)C`
`q_(2)+4muC=4xx10^(-6)C,r=0.15m`

x=location of null - point from `+1muC` charge
At null - point, the net electric field will be zero.
i.e. `E_(1)-E_(2)=0rArrE_(1)=E_(2)`
`rArr(1)/(4pi epsilon_(0))*(q_(1))/(x^(2))=(1)/(4piepsilon_(0))*(q_(2))/((0.15-x)^(2))`
`rArr((0.15-x)^(2))/(x^(2))=(4xx10^(-6))/(1xx10^(-6))`
`rArr(0.15-x)/(x)=2rArr0.15-x=2x`
`:." "x=(0.15)/(3)=0.05` m
So, the null - point is at a distance `0.05` m from `+muC` charge.