SS: Magnetic field due to current in a straight wire

Movement of electric charge is an underlying cause of magnetism. Hence, an electric current, being a flow of charge, produces a magnetic field. If the current is flowing in a wire, the shape of the magnetic field is dependent on the configuration of the wire.

The magnetic field lines produced by a current in a straight wire are in the form of circles with the wire as its centre.


magnetic field wire


Right-hand rule can be used to find the direction of the magnetic field produced due to current flow.

  • Right-hand rule: Grasp the wire with right hand so that the thumb points in the direction of the conventional current, then the wrapped fingers will encircle the wire in the direction of the magnetic field.


The magnetic field is strong in the region around the wire and weakens with increasing distance, i.e., the field lines near the wire are drawn closer to another. With increasing distances, concentric circles are further apart.


The larger the current, the stronger is the magnetic field.


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