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A bar magnet is released from rest alon...

A bar magnet is released from rest along the axis of a very long, vertical copper tube. After some time the magnet.

A

Will stop in the tube

B

Will move with almost contant speed

C

will move with an acceleration g

D

will oscillate.

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The correct Answer is:
**Step-by-Step Solution:** 1. **Understanding the Setup:** - We have a bar magnet that is released from rest along the axis of a very long vertical copper tube. The bar magnet has a North and South pole. 2. **Initial Condition:** - When the bar magnet is released, it starts to fall under the influence of gravity. Initially, it accelerates downward with an acceleration equal to the acceleration due to gravity (g). 3. **Induction of Eddy Currents:** - As the bar magnet falls, its magnetic field changes with respect to the copper tube. According to Faraday's law of electromagnetic induction, a changing magnetic field induces an electromotive force (EMF) in the conducting material (copper tube). This results in the generation of eddy currents within the copper tube. 4. **Direction of Eddy Currents:** - The induced eddy currents will flow in such a direction as to oppose the change in magnetic flux through the tube, as per Lenz's Law. This means that the eddy currents will create a magnetic field that opposes the motion of the falling magnet. 5. **Retarding Force on the Magnet:** - The eddy currents generate a retarding force that acts upward on the bar magnet. This force opposes the gravitational force acting downward on the magnet. 6. **Equilibrium Condition:** - As the magnet continues to fall, the retarding force due to the eddy currents increases. Eventually, the retarding force will become equal to the gravitational force acting on the magnet. 7. **Constant Velocity Motion:** - At the point where the retarding force equals the gravitational force, the net force acting on the bar magnet becomes zero. According to Newton's first law of motion, an object with zero net force will continue to move at a constant velocity. Therefore, the bar magnet will fall with a constant velocity through the copper tube. 8. **Conclusion:** - After some time, the bar magnet will move with a constant velocity as it falls through the copper tube. ---
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