How does a magnetic field induce an electromotive force in a moving conductor?

A magnetic field induces an electromotive force in a moving conductor through a process called electromagnetic induction.

Electromagnetic induction is a fundamental principle in physics, discovered by Michael Faraday in 1831. It describes the process by which a magnetic field can generate an electric current in a conductor. This happens when the magnetic field around a conductor changes, either because the conductor is moving through a stationary magnetic field, or because the magnetic field itself is changing around a stationary conductor.

The principle of electromagnetic induction is based on Faraday's law of electromagnetic induction. This law states that the electromotive force (EMF) induced in a circuit is directly proportional to the rate of change of magnetic flux through the circuit. In simpler terms, the faster the change in the magnetic field, the greater the induced EMF.

When a conductor moves through a magnetic field, the electrons within the conductor experience a force. This force pushes the electrons to move, creating an electric current. The direction of this induced current is given by Lenz's law, which states that the induced current will always be in a direction to oppose the change in magnetic flux that produced it.

For example, if a straight wire is moved upwards through a magnetic field directed into the page, the induced current will flow from the top of the wire to the bottom. This is because the upward motion of the wire decreases the magnetic flux through the circuit, and the induced current opposes this decrease by creating its own magnetic field directed out of the page.

In summary, a magnetic field can induce an electromotive force in a moving conductor through the process of electromagnetic induction. This process is governed by Faraday's law and Lenz's law, which together describe how a changing magnetic field can generate an electric current in a conductor.