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Question
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?
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Solution
The activity is as follows:
Take a small aluminum rod AB. Using two connecting wires suspend it horizontally from a stand, as shown in the figure given below.
A current- carrying rod AB experiences a force perpendicularto its length and the magnetic field
Place a strong horseshoe magnet in such a way that the rod lies between the two poles with the magnetic field directed upwards. For this put the North Pole of the magnet vertically below and the South Pole vertically above the aluminium rod.
Connect the aluminium rod in series with a battery, a key and a rheostat.
Now pass a current through the aluminium rod from end B to end A.
It is observed that the rod gets displaced towards the left due to the force experienced by it.
Fleming’s left-hand rule is used to find the direction of the force acting on the current carrying conductor. According to this rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular as shown in the diagram. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.
Fleming's left - hand rule
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