Magnetic Field of A Current

When electric current flows through a conductor, it produces a magnetic field around the conductor. This shows that electricity and magnetism are closely related. For a straight current-carrying wire, the magnetic field lines form concentric circles around the wire.

The direction can be found using the **right-hand grip rule**. Point the thumb of your right hand in the direction of conventional current. The curled fingers show the direction of the magnetic field around the wire.

The magnetic field becomes stronger when: current increases; the distance from the wire decreases. For a long straight conductor, the field strength is approximately: **B = μ₀I / 2πr** where: `B` = magnetic flux density `I` = current `r` = distance from the wire `μ₀` = permeability of free space

A coil containing many turns of wire is called a **solenoid**. When current flows through a solenoid, its magnetic field resembles that of a bar magnet. The field inside a long solenoid is relatively strong and nearly uniform.

An electromagnet can be made stronger by: increasing current; increasing number of turns; * adding a soft-iron core.