The electric current flows when there is a complete circuit, which means there is a closed loop for the electrons to flow through. In other words, the current flows when there is a path from the positive terminal of a battery or other voltage source, through a conducting material (like a wire), and back to the negative terminal.

When the circuit is open (i.e., there is a gap or break in the conducting path), the current stops flowing. This is because the electrons cannot complete the circuit and return to the negative terminal.

The amount of current that flows is determined by several factors, including the voltage of the source, the resistance of the conducting material, and the size of the gap in the circuit (if there is one).