How does an electric field affect free electrons in a conductor?

An electric field causes free electrons in a conductor to move, creating an electric current.

When an electric field is applied to a conductor, it exerts a force on the free electrons present in the conductor. These free electrons, which are negatively charged, are repelled by the negative terminal of the electric field and attracted towards the positive terminal. This movement of electrons constitutes an electric current.

The strength of the electric field determines the force exerted on the electrons. The stronger the field, the greater the force and the faster the electrons move. This is why a higher voltage (which creates a stronger electric field) results in a higher current. However, the movement of electrons is not just a simple straight line from the negative to the positive terminal. Electrons move in a random, zigzag pattern due to collisions with atoms in the conductor. This is known as drift velocity.

The drift velocity of the electrons is directly proportional to the electric field strength. This relationship is described by Ohm's law, which states that the current through a conductor between two points is directly proportional to the voltage across the two points, and inversely proportional to the resistance between them. The resistance in this case is determined by factors such as the conductor's material, length, and temperature.

In addition to causing movement, the electric field also imparts energy to the electrons. This energy is transferred to the conductor's atoms during collisions, causing them to vibrate more vigorously. This increase in vibration is perceived as a rise in the conductor's temperature, which is why conductors heat up when a current passes through them.

In summary, an electric field affects free electrons in a conductor by causing them to move (creating an electric current), determining their speed (via the field's strength), and imparting energy to them (which can cause the conductor to heat up). Understanding these effects is crucial for many applications in physics and engineering, from designing electronic circuits to understanding the behaviour of plasmas in fusion reactors.