Question

Which of the following are true? Check all that apply. (1) If the net electric field at a particular location inside a piece of metal is zero, the metal is not in equilibrium. (2) The net electric field inside a block of metal is zero under all circumstances. (3) The net electric field at any location inside a block of copper is zero if the copper block is in equilibrium. (4) The electric field from an external charge cannot penetrate to the center of a block of iron. (5) In equilibrium, there is a net flow of mobile charged particles inside a conductor.

Short answer

The correct option is (3), The net electric field at any location inside a block of copper is zero if the copper block is in equilibrium.

Step-by-step solution

Significance of the electric field

The electric field is referred to as a region in which a charged particle can exert force on another charged particle.

The net electric field of the metal is zero when the metal is in the equilibrium state but in any other state, the net electric field of the metal cannot be zero.

Identification of the correct statement

Statement (1) is incorrect as the net electric field of the metal is zero when the metal is in the equilibrium state. But here, the metal is not in an equilibrium state.

Statement (2) is incorrect as in only equilibrium state, the net electric field in the metal is zero, except this, the net electric field is not zero.

Statement (4) is incorrect as the induced charges mainly cancel the different external fields but the external “electric field” is able to penetrate conductors and hence it can penetrate to the center of the block of iron.

Statement (5) is incorrect as no net electric field acts during the equilibrium state, hence, no force acts to move the different types of mobile charges and no flow of the mobile charges occurs.

Statement (3) is correct as the net electric field in the metal is zero when it is in an equilibrium state. So, the net electric field at any location inside a block of copper is zero if the copper block is in equilibrium (copper is a metal).

Thus, the correct option is (3), The net electric field at any location inside a block of copper is zero if the copper block is in equilibrium.