Here's why:
* Electrons are negatively charged: This charge allows them to be easily moved by an electric field.
* Electrons are located in the outer shell of an atom: This makes them relatively loosely bound to the atom and easier to move.
* Conductors have loosely bound electrons: Metals and other conductive materials have electrons that can easily detach from their atoms and move freely throughout the material.
When a voltage is applied across a circuit, it creates an electric field that pushes the free electrons in the conductor. This flow of electrons constitutes an electric current.
Important Note: While protons are positively charged, they are located in the nucleus of the atom and are much more strongly bound. They don't typically move freely through a circuit.
