Some questions about the balance of physical static points

1.The electric potential of the earth is zero, when the cuboid metal body comes into contact with the ground, the earth and the cuboid metal body become a whole, and when the electrostatic equilibrium is reached, the electric potential becomes zero.

2 When not grounded, the cuboid metal body is in the electric field formed by a positive charge, so the electric potential is positive.

3.When the cuboid metal body comes into contact with the ground, the electrons in the earth will move directionally towards the cuboid metal body under the action of the electric field force until the electrostatic equilibrium is reached. It should be noted here that it is the whole composed of the earth and the rectangular metal body that achieves electrostatic equilibrium.

4 The entire conductor that reaches electrostatic equilibrium is an equipotential body and should include the surface.

1.A ground potential of 0 is defined, in fact, the point of the potential 0 can be arbitrarily selected.

2.Not grounding is certainly not 0. Moving the charge +q from infinity to a metal body requires work to overcome mutual resistance.

3.Your understanding is very skewed. The combined field strength of the metal plate is not so large as the field strength of +q outside the metal body, but is equal to the field strength of +q in the metal body (+q is distributed on the outer surface of the metal body).

After grounding, the charge is redistributed (including the charge on the metal plate) so that the electrostatic equilibrium is still satisfied to satisfy the condition that the electric potential is 0. You don't give the conductor shape, so you can't calculate it concretely.

4.The electric potential is not determined by the charge itself being charged, but by the electric field formed by the other charges here, so the whole conductor is an equipotential body, and you are obviously misled by the point charge potential formula.

The book must be right.

It should be understood as a metal body, it will be shielded, so its entire electric potential is 0 Thinking in this direction, I forgot about it for too long, hehe.

This is the so-called Earnshaw's theorem, the bright condition of the stable equilibrium of the particle is that the electrostatic energy has a local minimum, but the electric potential is a harmonic function, and there can be no local extremum, so the particle cannot be stable equilibrium in the electrostatic field.

The electrostatic field refers to the electric field observed by the observer when the charge is relatively static. It is a special form of matter that exists in the space around the charge, and its basic characteristic is the powerful action on the stationary charge placed in the conjure, which is described by Coulomb's law.

<> the second question was not completed, the length relationship was not given, and it could not be answered.