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Two charges q and 3q are separated by a distance ‘r’ in air. At a distance x from charge q, the resultant electric field is zero. The value of x is :

1. ( ) 3 1 3 r +
2. ( ) r 3 1 +
3. ( ) 3 1 r +
4. r ( ) 3 1 +

Correct answer: ( ) 3 1 r +

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