Q.

A thin metallic wire having cross-sectional area of 10-4 m2 is used to make a ring of radius 30 cm. A positive charge of 2π C is uniformly distributed over the ring, while another positive charge of 30 pC is kept at the centre of the ring. The tension in the ring is ____ N; provided that the ring does not get deformed (neglect the influence of gravity).

(Given, 14πϵ0=9×109 in SI units)                       [2024]


Ans.

(3)

2Tsindθ2=kq0R2·λRdθ                    [λ=Q2πR]

T=kq0Q(R2)×2π

=(9×109)(2π×30×10-12)(0.30)2×2π 

=9×10-3×309×10-2=3N