When a conducting sphere with a cavity is placed in an electric field, the electric field inside the cavity remains zero if no charge is introduced into the cavity. The free electrons in the conducting material respond to the external field, ensuring that the net electric field within the metal is also zero. Although the sphere itself is electrically neutral, induced charges will appear on the outer surface of the sphere, with a distribution that depends on the external field. If a charge is placed inside the cavity, it will create an electric field, but otherwise, the cavity remains unaffected. Thus, the presence of an external electric field does not alter the conditions inside the cavity unless additional charges are introduced.
