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Three charge q , Q and -4q are placed in...

Three charge `q , Q` and `-4q` are placed in a straight line , line of length `L`at points distant `0 ,L//2` and `L` respectively from one end. In order to make the net force on `q` zero, the charge `Q` must be equal to

A

`- q`

B

`- 2 q`

C

`(-q)/(2)`

D

q

Text Solution

Verified by Experts

The correct Answer is:
A
`(F_("Net"))_(q) = 0`
`rArr k (Q q)/(((l)/(2))^(2))+ k ( 4 q ^(2))/( l^(2)) = 0`
where ` k = (1)/( 4 pi epsilon_(0)) rArr 4 Q q + 4 q^(2) = 0 rArr Q = - q `
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Knowledge Check

  • Three charges 4q, Q and q are in a straight line in the position of 0. l//2 and l respectively. The resultant force on q will be zero, if Q=

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