Why conductors resist current

The idea

Electrons in a conductor are not completely free: the attraction of the atoms among which they move restrains them, so their motion is retarded by the conductor's resistance.

A crowded path

In a metal wire the electrons move among the atoms of the metal. When a cell is joined, they drift along the wire.

What do you think holds the electrons back as they move through a conductor?

• The attraction of the atoms among which they move
• The colour of the metal
• The weight of the electrons pulling them down

Electrons and atoms

Press Next step to see what the atoms do to the moving electrons.

Resistance at work

The electrons are not completely free. The atoms attract them, so their motion is held back. This holding back is what we call the resistance of the conductor.

Electrons in a conductor are not completely free: the attraction of the atoms among which they move restrains them, so their motion is retarded by the conductor's resistance.

Notes

Electrons in a conductor are not completely free: the attraction of the atoms restrains them, so their motion is retarded by the conductor's resistance.

Check yourself

Why are the electrons in a conductor not completely free to move?

What happens to the motion of electrons through a conductor because of its resistance?

In the picture the electrons wander along a slowed path among the atoms. What does this show?

• The atoms among which they move attract and restrain them — correct. Yes!
• The electrons have no charge. Electrons carry a negative charge. It is the attraction of the atoms that restrains them.
• The potential difference is too large. A potential difference sets the charges in motion. It is the attraction of the atoms that restrains them.
• It is made faster. The resistance retards the motion of the electrons, slowing them down.
• It is retarded — correct. Yes!
• It stops for ever. The electrons are held back, not stopped. They still drift along, which is how the current flows.
• The conductor has no atoms. The grey circles stand for the atoms of the conductor. Their attraction retards the electrons.
• The electrons move without any hindrance. They are not completely free to move. The atoms restrain them, and that is the resistance.
• The conductor resists the flow of charge — correct. Yes!