Assume we’re holding a current-carrying straight conductor in our right hand, with the thumb pointing in the current’s direction. The right-hand thumb rule states that our finger should wrap around the conductor in the direction of the magnetic field lines. Consider a current flowing in an east-west direction across a horizontal power line. The magnetic field at a position above the wire is directed north to south using the right-hand thumb-rule. At a position directly above the wire, the magnetic field is directed from south to north.The compass needle deflects in the north-south direction when a magnetic compass is placed below in the current-carrying cable.

• The magnetic field is a field generated by the electric charge or magnet in the motion.
• The magnetic field is the area around the moving electric charge or magnetic substance within which the force of magnetism operates.
• Using magnetic field lines, magnetic fields are described.
• It is a visual method used to visualise the path of the magnetic field and its strength.