A thin wire of radius r has an electric charge q. What will be the increment of the force stretching the wire if a point charge q0 is placed at the ring's centre ??
Pls explain the question 2..
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1 Answers
106Let the tension in the string before the charge q0 was put be T and final tension be T'
Consider a small arc which subtends an angle dθ at the centre of the ring.
Writing force equations for that part and using superposition of forces we have
2T'*sin(dθ/2) = 2T*sin(dθ/2) + qo*(Rdθ*q/2ΠR)/4Πε0R2
Now, sin(dθ/2)~dθ/2
So, (T'-T)dθ = qoqdθ/8Π2εoR2
So, T'-T = increment in tension = qoq/8εoΠ2R2
