Engineering
Physics
SI Units
Electric Flux and Gauss Law and its Applications
Electric Potential Energy and Electric Potential
Question

Electric potential at a point P, r distance away due to a point charge q at point A is V. If twice of this charge is distributed uniformly on the surface of a hollow sphere of radius 4r with centre at point A, the potential at P now is V/n then write value of n 

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Solution
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The electric potential due to a point charge q at a distance r is given by V = kq/r. When the charge is doubled to 2q and distributed uniformly on a hollow sphere of radius 4r, the potential at any point outside the sphere is the same as that of a point charge at its center. Therefore, the new potential at point P (distance r from center) is V' = k(2q)/r = 2(kq/r) = 2V. The problem states this new potential is V/n, so V/n = 2V, meaning n = 2.

Point Charge Potential: V=kqr

Sphere Potential (outside): V=k(2q)r=2V

Final Answer: 2