A point charge Q is located in a cavity within an isolated conducting sphere. Point A is inside the cavity; B and C are outside the sphere at equal distances from the sphere's centre. Compare the electric-field magnitudes Eₐ, Eᵦ and E𝒸. Image
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Question

A point charge Q is located in a cavity within an isolated conducting sphere. Point A is inside the cavity; B and C are outside the sphere at equal distances from the sphere's centre. Compare the electric-field magnitudes Eₐ, Eᵦ and E𝒸. Image

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G1 Physics · Accepted Answer

Step 1: In electrostatic equilibrium the electric field inside the conducting material is zero, but the charge inside a hollow cavity produces a generally nonzero field in the cavity. Step 2: Since A lies inside the cavity (not inside the metal), Eₐ need not vanish; in this arrangement Eₐ ≠ 0. Step 3: An isolated spherical conducting outer surface is an equipotential sphere. Step 4: Outside, its electrostatic field is radially symmetric and depends only on distance from the centre (for a spheri…