Describe the activity to show that a current-carrying conductor experiences a force perpendicular to its length in an external magnetic field.

Explanation

i] To show that a current-carrying conductor placed in a magnetic field experiences a force perpendicular to its length :
Figure : Experiment to study force on a current carrying conductor in a magnetic field
1] Take an aluminium rod AB (of length about 5 cm) and suspend it horizontally from a stand using two connecting wires as shown in the figure.
2] Connect the two ends of the wire in series with a battery and a plug key.
3] Place a strong horse- shoe magnet in such a way that its north pole lies below and south pole above the aluminium rod as shown. Then, the magnetic field will be directed upwards.
4] Inset the plug key so that current flows through the aluminium rod from A to B. Notice the movement of the rod .
5] Hold the magnet at different angles to the rod and observe the change .
Inference : When current flows, the aluminium rod gets displaced because of the force acting on it due to magnetic field of the horse shoe magnet. It is observed that the displacement of the rod is largest or the force on it is maximum when the direction of current is perpendicular to the direction of the magnetic field . A current-carrying conductor experiences a force perpendicular to its length in a external magnetic field .
ii] Fleming.s left-hand rule: Fleming.s left hand rule gives the direction of the force experienced by a straight current carrying conductor placed in a magnetic field . According to this rule, if the thumb, fore-finger and middle finger of the left hand are stretched to be perpendicular to each other as shown in the figure , and if the force finger represents the direction of magnetic field , the middle finger represents the direction of current, then the thumb represents the direction of force.