Describe the activity that shows that a current-carrying conductor experiences a force perpendicular to its length and the external magnetic field. How does Fleming's left-hand rule help us to find the direction of the force acting on the current carrying conductor?

Explanation

Take a small rod (AB) os aluminium an suspend it with a stand , using two connecting wires.
(i) Take a horse-shoe magnet and keep it in a way that its magnetic field is in upward direction. For this, the North Pole should be at the bottom and South Pole should be at the top. The aluminium rod should be between the two poles of this magnet.

(ii) Now connect the aluminium rod to a battery and plug key so that current flow through it from B to A.
(iii) You will notice that the aluminium rod moves towards left.
(iv) Now, change the direction of current from A to B.
(v) In this case the aluminium rod moves towards right.
In this experiment, directioon of current and direction of magnetic field are mutually perpendicular. Direction of movement of aluminium rod is perpendicular to direction of current and direction of magnetic field

Fleming.s left hand rule : If the thumb, index finger and ring finger of left hand are kept in mutually perpendicular direction then index finger shows the direction of magnetic field, ring finger shows the direction of eletric current and thumb shows the direction of deflection in current carrying conductor . By using this rule, we can easily find the direction of deflection.