18. Two small spheres each having a...
Question

# 18. Two small spheres each having a charge +Q are suspended by insulating threads of length L from a hook. This arrangement is taken to a space where there is no gravitational effect, then the angle between the two threads and the tension in each will be :- 1 Q? 4Tɛo (2L)2 Q2 (1) 1800_1 (Z '4ntɛ, L (3) 180°, ame, (4) 180°. alle,

NEET/Medical Exams
Physics
Solution
73
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Let us consider a small element of the ring between the points ( mathrm{M} ) and ( mathrm{N} ) having a charge dQ. The fleld at P due to this element is ( d E=frac{d Q}{4 pi in_{0}(M P)^{2}} ) the component of ( d E ) along OP is ( d E cos theta=frac{d Q}{4 pi in_{0}(M P)^{2}}left(frac{O P}{M P}right)=frac{x d Q}{4 pi in_{0}left(R^{2}+x^{2}right)^{3 / 2}} ) The net field at ( P ) is ( E=int d E cos theta ) ( =int frac{x d Q}{4 pi in_{0}left(R^{2}+x^{2}right)^{3 / 2}}=frac{x Q}{4 pi in_{0}left(R^{2}+x^{2}right)^{3 / 2}} )