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A particle of charge '–q' and mass 'm' moves in a circle of radius 'r' around an infinitely long line charge of linear charge density '+ λ '. Then time period will be given as : (Consider k as Coulomb's constant)

1. T = q k 2 m r 2 1 λ π
2. T 2 = q k 2 m 4 2 λ π r 3
3. T = 2 π r q k 2 m λ
4. T = m q k 2 2 1 λ π

Correct answer: T = 2 π r q k 2 m λ

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