Question 605: Electrostats & Capacitance

Question

Three charges + Q, q, + Q are placed respectively, at distance, 0, d/2 and d from the origin, on the  x-axis. If the net force experienced by + Q, placed at x = 0, is zero, then value of q is :

Accepted Answer

Force on + Q charge at x = 0 due to q charge, F
1
= $${{KQq} \over {{{\left( {{d \over 2}} \right)}^2}}}$$
Force on +Q charge at x = 0 due to + Q charge at x = d is,
F
2
= $${{KQQ} \over {{d^2}}}$$
According to the question,
F
1
+ F
2
= 0
$$ \Rightarrow $$   F
1
= $$-$$ F
2
$$ \Rightarrow $$   $${{KQq} \over {{{\left( {{d \over 2}} \right)}^2}}}$$ = $$-$$ $${{KQQ} \over {{d^2}}}$$
$$ \Rightarrow $$   4q = $$-$$ Q
$$ \Rightarrow $$   q = $$-$$ $${Q \over 4}$$

Answer

$$-$$ $${Q \over 4}$$

Answer

+ $${Q \over 2}$$

Answer

+ $${Q \over 4}$$

Answer

$$-$$ $${Q \over 2}$$

Electrostats & Capacitance

Three charges + Q, q, + Q are placed respectively, at distance, 0, d/2 and d from the origin, on the x-axis. If the net force experienced by + Q, placed at x = 0, is zero, then value of q is :

Choose the correct answer: