If the conductor is placed in an electric field with an electric field intensity of e, the free electrons in the conductor will move against the electric field under the action of the electric field force. In this way, the negative charge of the conductor is distributed on one side and the positive charge is distributed on the other side, which is the phenomenon of electrostatic induction. Due to the redistribution of the charges in the conductor, these charges form another electric field in the opposite direction to the external electric field, and the electric field intensity is within E. According to the principle of field strength superposition, the electric field intensity in the conductor is equal to the superposition of the outside and inside of E. When the total electric field intensity in the conductor is zero, the free electrons in the conductor no longer move. In physics, the state in which there is no charge movement in a conductor is called electrostatic balance. In an electrostatically balanced conductor, the internal electric field intensity is zero everywhere. It can be inferred that the charge of the conductor in electrostatic balance is only distributed on the outer surface of the conductor. If this conductor is hollow, when it reaches electrostatic balance, there will be no electric field inside. In this way, the shell of the conductor will play a "protection" role in its interior, so that its interior is not affected by the external electric field. This phenomenon is called electrostatic shielding.

No matter how much electricity is brought outside, there is no electric field inside.

If there is a charge in the cavity, there will be a cavity conductor interacting with it to generate an electric field.

Finally, the whole outer wall has different charges at the proximal end and the same charge at the distal end, and the inner wall is uncharged due to electrostatic balance.