When a conductor is placed in an external electric field,

The correct answer is Option (4) → The electric field produced inside the conductor is equal and opposite to the external electric field.

In electrostatic equilibrium the field inside the material of a conductor must be zero; otherwise its free electrons would keep moving.

In an external field the free electrons shift to one side, leaving the other side positive. These induced surface charges set up a field that grows until it exactly cancels the external field inside.

    \( \vec{E}_{\mathrm{induced}} = -\vec{E}_{\mathrm{ext}} \)
    \( \vec{E}_{\mathrm{net}} = \vec{E}_{\mathrm{ext}} + \vec{E}_{\mathrm{induced}} = 0 \)

Why the other options are incorrect

• Option (1) The electric field produced inside the conductor is greater than the external electric field. — Incorrect. The net field inside would then be non-zero, against the external field.

• Option (2) The electric field produced inside the conductor is smaller than the external electric field. — Incorrect. Partial cancellation happens in a dielectric, whose charges cannot move freely; in a conductor it is complete.

• Option (3) The electric field produced inside the conductor is the same as the external electric field. — Incorrect. A field in the same direction would double the field inside, not cancel it.

NCERT (2026-27):
Dielectrics and Polarisation – “… Recall from Section 2.9 what happens when a conductor is placed in an external electric field. The free charge carriers move and charge distribution in the conductor adjusts itself in such a way that the electric field due to induced charges opposes the external field within the conductor. This happens until, in the static situation, the two fields cancel each other and the net electrostatic field in the conductor is zero. … Unlike in a conductor, however, the opposing field so induced does not exactly cancel the external field. It only reduces it.”