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The charges Q, +q and + q are placed at ...

The charges Q, +q and + q are placed at the vertices of an equilateral triangle of side l . If the net electrostatic potential energy of the system is zero , the Q is equal to

A

`+q//2`

B

zero

C

`-q//2`

D

`-q`

Text Solution

Verified by Experts

The correct Answer is:
C
Potential energy A due to
`B=(1)/(4piepsilon_(0))*(q^(2))/(a)`
Potential energy of B due to
`C=(1)/(4piepsilon_(0))*(Qq)/(q)`.
Potential energy of C due to `A=(1)/(4piepsilon_(0))*(Qq)/(a)`.
`therefore` Total potential energy `=(1)/(4piepsilon_(0))*(q^(2))/(a)+(2Qq)/(4piepsilon_(0)a)=0`.
Therefore Q has to be negative .
`q^(2)=-2QqrArrQ=-q//2`.
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