Question

A 31 mC charge is positioned on the x axis at x + 8 cm. Where should a -70 mC charge be placed (on the positive X-axis) to produce a net electric field of zero at the origin?

Answer 1

Answer:r=12.02 cm

Step-by-step explanation:

Given

`q_1=31 mC=31* 10^(-3)C`

Placed at x=8 cm

`q_2=-70 mc=-70* 10^(-3) C`

placed at a distance, suppose r

Electric field due to positive charge will be away from the origin and electric field due to negative charge is towards the origin

Thus net effect will be zero

`E=(kq)/(r^2)`

`E_1=(9* 10^(9)* 31* 10^(-3))/(0.08^2)`

`E_2=(9* 10^(9)* 70* 10^(-3))/(r^2)`

Equate
`E_1=E_2`

`(31)/(8^2)=(70)/(r^2)`

`r=8* \sqrt{(70)/(31)}`

r=12.02 cm