Question

2 point charges +2µc and –3µc are placed at
points (1, 2, 3) & (2, 3, 4). Find the force on the
– ve charge due to the +ve charge in vector form
(given that the medium is vacuum).

Answer 1

Answer:

Let a charge q be placed at 0, as shown in Fig.

Now, `vec(F)_(AB) = (q_(1) q_(2))/(4pi in_(0) AB^(2))`

`= (9xx10^(9)xx(2xx10^(-6))(3xx10^(-6)))/((0.20)^(2))`

`vec(F)_(AB) = 1.35N`, along AB

`vec(F)_(AC) = (q_(1) q_(2))/(4pi in_(0) AC^(2)) = (9xx10^(9)xx(2xx10^(-6))(3xx10^(-6)))/((0.20)^(2))`

= 1.35N, along AB

`vec(F)_(AO) = (q_(1) (q))/(4pi in_(0) AO^(2)) = (9xx10^(9) (2xx10^(-6)) q)/((sqrt(3) xx 10^(-1))^(2))`

`= 6xx10^(5)` q, along OA, when q is positive For equilibrium of charge at A,

`F_(AB) cos 30^(@) + F_(AC) cos 30^(@) = F_(AO)`

`1.35 (sqrt(3))/(2) + 1.35 xx(sqrt(3))/(2) = 6xx10^(5)q`

`:. q = (1.35 sqrt(3))/(6xx10^(5)) = 0.3897xx10^(-5) C = 3.897 muC`