What is the opposition to electric current called?

The opposition to the flow of electric current in a conductor is called electrical resistance.

Resistance is a measure of how much a material resists or restricts the movement of electric charges (electrons). It depends on factors such as the material of the conductor, its length, cross-sectional area, and temperature.

Mathematically, resistance is expressed using Ohm’s Law:
R = V / I
where R is resistance, V is voltage (potential difference), and I is current.

The unit of resistance is ohm (Ω).

A higher resistance means less current flows through the conductor, while a lower resistance allows more current to pass easily.