The Reason Why the Bar Magnet Does Not Fall Under Gravity When Held Firmly by a Vertical Iron Sheet

There are two possible explanations as to why a bar magnet does not fall under gravity when held firmly by a vertical iron sheet. Let's examine each one and determine which one is correct.

Explanation 1: The Force of Magnetic Attraction is Equal and Opposite to its Weight

According to this explanation, the force of magnetic attraction between the bar magnet and the iron sheet is equal in magnitude and opposite in direction to the weight of the magnet. This balance of forces prevents the magnet from falling under gravity.

Explanation 2: The Force of Static Friction Between the Iron Sheet and the Magnet is Equal to the Weight of the Magnet

This explanation suggests that the force of static friction between the iron sheet and the magnet is equal in magnitude to the weight of the magnet. This frictional force opposes the gravitational force, thereby preventing the magnet from falling.

Determination of the Correct Explanation

While both explanations may initially seem plausible, a closer examination reveals that only the first explanation is correct. Let's delve into the details to understand why.

When the bar magnet is held firmly by the vertical iron sheet, it does not experience any horizontal motion. This means that the force of static friction between the magnet and the iron sheet must be equal and opposite to the force applied on the magnet due to its weight. If the frictional force were less than the weight, the magnet would slide down. Conversely, if the frictional force were greater than the weight, the magnet would move upwards.

However, the force of static friction is a result of the electromagnetic interaction between the atoms of the magnet and the iron sheet. It is not directly related to the magnetic attraction between the magnet and the iron sheet. Therefore, the second explanation, which suggests that the force of friction is equal to the weight of the magnet, is incorrect.

On the other hand, the force of magnetic attraction between the magnet and the iron sheet is indeed equal and opposite to the weight of the magnet. This is due to the fundamental nature of magnetic fields and the interaction between magnetic poles. The magnet is held firmly in place by the magnetic force, which balances the gravitational force acting on it.

Conclusion

In conclusion, the reason why a bar magnet does not fall under gravity when held firmly by a vertical iron sheet is that the force of magnetic attraction between the magnet and the iron sheet is equal and opposite to the weight of the magnet. This balance of forces ensures that the magnet remains in place without any horizontal motion.