In electrostatic equilibrium, what is the electric field inside a conductor?

In electrostatic equilibrium, what is the electric field inside a conductor?

• A. E = σ/ε0
• B. E = ∞
• C. E = 0
• D. E = k Q / r^2

Answer: (C)

In electrostatic equilibrium, the free charges in a conductor rearrange themselves until there is no net electric field inside. If any field were present, it would push charges to move, breaking the equilibrium. The result is that the electric field inside a conductor is zero, and the potential throughout the conductor is the same. All excess charge sits on the surface, which is why the field outside can be nonzero while the interior field remains zero. The other expressions describe different situations. σ/ε0 gives the field just outside a charged surface, not inside. An infinite field isn’t physically required here, and the inverse-square form kQ/r^2 describes the field of a point charge, not the interior of a conducting solid in equilibrium.

In electrostatic equilibrium, the free charges in a conductor rearrange themselves until there is no net electric field inside. If any field were present, it would push charges to move, breaking the equilibrium. The result is that the electric field inside a conductor is zero, and the potential throughout the conductor is the same. All excess charge sits on the surface, which is why the field outside can be nonzero while the interior field remains zero.

The other expressions describe different situations. σ/ε0 gives the field just outside a charged surface, not inside. An infinite field isn’t physically required here, and the inverse-square form kQ/r^2 describes the field of a point charge, not the interior of a conducting solid in equilibrium.