Whenever the current is passed through a conductor magnetic lines of force are set up around the conductor, this effect of current is known as the magnetic effect of current.
What is an electromagnet?
The magnet which works on the principle of magnetic effect of current is known as the electromagnet.
State the different methods of determining the direction of magnetic flux around a current-carrying conductor.
The direction of the magnetic lines Of force around a current carrying conductor can be determined by these following methods:
(a) Right hand rule.
(b) Maxwell’s cork screw rule.
(c) End rule or arrow rule.
(d) By means of the magnetic compass.
Right hand rule
As shown in Fig. 11.13 a long conductor AB is carrying current in the direction as marked. The direction of the lines of force can be determined, hold the conductor in your right hand so that the thumb indicates the direction of the current in the conductor than the wrapped fingers will indicate the direction of the lines of force around the conductor.
Fig. 11.13. Right hand rule.
Maxwell’s cork screw rule
Generally it is known as the screw rule. Imagine a right handed wood screw as shown in Fig. 11.14. Now rotate the screw so that the tip or point should indicate the direction of current then the direction of rotation will indicate the direction of magnetic lines of force around the conductor.
Fig. 11.14. Cork’s screw rule.
End rule or arrow rule
This method is commonly employed for finding out the direction Of lines Of force around a current carrying conductor. The direction is observed from one end. If the current is going away from the observer this is marked as + and if coming towards the observer it is marked as • sign.
Now the direction Of magnetic lines of force will be anticlockwise if the current has + direction i.e., coming towards the observer and it will have clockwise direction, if the current is going away from the observer i.e. + sign as shown in Fig. 11.15.
Fig. 11.15. End rule.
By means of the magnetic compass
A magnetic compass is placed around a conductor which is live or carrying current, then the north pole of the magnetic needle will indicate the direction of magnetic lines of force around the conductor.