Question

Satrajit had learned in electrostatics that the electric field inside a conductor is always zero. Now they are telling him that when current flows, an electric field gets set up inside a conductor which drifts the electrons, thus making the current flow. This makes no sense to him.
It makes no sense to him because

• A. They are telling him some random things which has no science in it
• B. He doesn’t understand that electric field inside a conductor is zero only under electrostatic conditions
• C. He thinks electric field is non conservative.
• D. He thinks electric field is not a vector.

Answer 1

The correct option is B He doesn’t understand that electric field inside a conductor is zero only under electrostatic conditions

Whenever a conductor is placed in an electric field, the free electrons experience a force on them due to this field and they move to the edges of the conductor against the field (since they are negatively charged. This sets up a new field inside the conductor due to negative charge accumulation on one side of the conductor (and hence positive on the other). This internal field opposes the external field and the electrons move until this field becomes equal and opposite to the external field and the net force on them is zero.
So once the charges have stopped moving, the electric field inside the conductor is zero.
But what happens when the electrons just keep moving under an external field and are unable to set up an opposite field because there is some device causing them to flow around in a loop? That is exactly what happens in an electrical circuit. A current gets set up in the circuit.
In other words, the electric field being zero inside a conductor is true only in an electrostatic condition.