An electric current is the flow of charge in a conductor when there is a potential difference between its ends - Leaving Cert Physics - Question 8 - 2013

An example of a conductor is copper, which is widely used in electrical wiring due to its excellent conductivity.

A common source of potential difference is a battery. Batteries convert chemical energy into electrical energy, creating a voltage difference.

In semiconductors, the charge carriers are electrons and holes. Electrons are negative charge carriers, while holes represent the absence of an electron, acting as positive charge carriers.

The I-V graph in the diagram represents an ohmic conductor, which is characterized by a linear relationship between current (I) and voltage (V).

A magnetic field is a region around a magnetic material or a moving electric charge within which the force of magnetism acts. It can be described in terms of its strength and direction.

To demonstrate that a long straight wire carrying a current produces a magnetic field, set up a circuit with a battery and a long straight wire. As current flows through the wire, place a small compass near the wire. The compass needle will deflect, indicating the presence of a magnetic field.

Sketch of the magnetic field:
The magnetic field lines will form concentric circles around the wire, with the direction determined using the right-hand rule: when the thumb points in the direction of current flow, the curled fingers indicate the direction of the magnetic field lines.

One application of the magnetic field due to a current is in electric motors. Electric motors use the magnetic field generated by current flowing through coils to produce rotational motion.