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Question -

Two charged conducting spheres ofradii a and b are connected to each other bya wire. What is the ratio of electric fields at the surfaces of the twospheres? Use the result obtained to explain why charge density on the sharp andpointed ends of a conductor is higher than on its flatter portions.



Answer -

Let a be the radius of asphere A, QA be the charge on the sphere, and CA bethe capacitance of the sphere. Let b be the radius of a sphereB, QB be the charge on the sphere, and CB bethe capacitance of the sphere. Since the two spheres are connected with a wire,their potential (V) will become equal.

Let EAbe the electric field ofsphere A and EB be the electric field of sphere B. Therefore,their ratio,

Putting the value of (2) in (1), we obtain

Therefore, the ratio ofelectric fields at the surface is

A sharp and pointed end can be treated as asphere of very small radius and a flat portion behaves as a sphere of muchlarger radius.Therefore, charge density on sharp and pointed ends of theconductor is much higher than on its flatter portions.

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