Here you should accurately understand the meaning of the topic! -The electric field intensity at any point inside the guide body! Because when the conductor is in electrostatic balance, the electric field intensity at any point inside the conductor is zero, so the electric field intensity of the conductor remains unchanged during the negative charge moving to the conductor!

Because of the electric field strength of the conductor, the potential of the conductor is equal to 0! Now, because the negative charge moves near the conductor, the negative charge will produce a negative potential at the position of the conductor. According to the principle of potential superposition, the potential of the conductor is negative, so the potential of the conductor becomes smaller! . . . . . . . . . good