Oersted Experiment: How Electricity Creates Magnetic Fields

The Oersted Experiment

The Oersted experiment involves placing a compass on a cord or wire. When no electric current flows through the wire, the compass needle points north, as it is guided by the Earth's magnetic field. However, when the cable is connected to an electrical generator (e.g., a battery), the compass needle deflects and becomes oriented perpendicular to the cable.

This phenomenon occurs regardless of the wire's orientation. Furthermore, if the direction of the current flowing through the cable is reversed, the compass needle will turn around, orienting itself perpendicular to the wire in the opposite direction.

The Discovery of Electromagnetism

This experiment demonstrates that an electric current creates a magnetic field around it. This reveals a strong relationship between electricity and magnetism. The branch of physics that studies this relationship is known as electromagnetism.

We will examine the magnetic fields created by currents in wires arranged in various forms and identify the lines of force within these fields.

Magnetic Field Created by a Straight Wire

The lines of force of the magnetic field created by an electric current passing through a straight piece of wire (or thread) are concentric circles. These lines are located in a plane perpendicular to the wire, with the center at the point where the plane intersects the cable.

The Right Hand Rule

To determine the direction of these lines of force, we apply the right hand rule. This consists of surrounding the cable with your right hand so that the extended thumb points in the direction of the electric current. In doing so, the other four fingers will point in the direction of the magnetic field lines created by the current.

Magnetic Field Created by a Loop

A loop is a conductor (or wire) that has been folded to form a closed figure, such as a:

• Circle
• Square
• Rectangle
• Triangle
• Pentagon

The ends of the cable are not attached to each other; instead, they are connected to the terminals of an electrical generator to allow an electric current to pass through the wire.