Magnetic Effect of Electric Current
When an electric current flows through a conductor, magnetic field is set up all along the length of the conductor. Fig. shows the magnetic field produced by the current flowing in a straight wire. The magnetic lines of force are in the form of concentric circles around the conductor.
The direction of lines of force depends upon the direction of current and may be determined by right-hand rule.Hold the conductor in the right-hand with the thumb pointing in the direction of current (See Fig. 7.12). Then the fingers will point in the direction of magnetic field around the conductor.
Applying this rule to Fig., it is clear that when viewed from left-hand side, the direction of magnetic lines of force will be clockwise.
The following points may be noted about the magnetic effect of electric current :
(i) The greater the current through the conductor, the stronger the magnetic field and vice-versa.
(ii) The magnetic field near the conductor is stronger and becomes weaker and weaker as we move away from the conductor.
(iii) The magnetic lines of force around the conductor will be either clockwise or anticlockwise, depending upon the direction of current. One may use right-hand rule to determine the direction of magnetic field around the conductor.
(iv) The shape of the magnetic field depends upon the shape of the conductor.