Ampère’s Law

Parallel wires carrying current produce magnetic fields, which in turn produce magnetic forces on currents. The first person to discover evidence that electricity and magnetism are related phenomena was H. Ch. Ørsted. Ørsted noticed that a wire carrying current was able to deflect a compass needle. Another physicist A. M. Ampère found that the magnetic fields created by parallel current-carrying wires interact with one another. The force felt between two parallel conductive wires nowadays is used to define the ampere (a unit of electrical current). Ampère was able to mathematically describe this type of magnetic force between electric currents, formulating what is known as Ampère’s law.

If the currents are in the same direction, the force attracts the wires. If the currents are in opposite directions, the force repels the wires. Magnets in which the magnetic field is produced by an electric current we call electromagnets. They are widely used in many electrical devices.