Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R
Assertion (A): A bar magnet dropped through a metallic cylindrical pipe takes more time to come down compared to a non-magnetic bar with same geometry and mass.
Reason (R) : For the magnetic bar, Eddy currents are produced in the metallic pipe which oppose the motion of the magnetic bar.
In the light of the above statement, choose the correct answer from the options given below :
Assertion (A): A bar magnet dropped through a metallic cylindrical pipe takes more time to come down compared to a non-magnetic bar with same geometry and mass.
Reason (R) : For the magnetic bar, Eddy currents are produced in the metallic pipe which oppose the motion of the magnetic bar.
In the light of the above statement, choose the correct answer from the options given below :
- Both A and R are true and R is the correct explanation of A
- A is false but R is true
- Both A and R are true but R is NOT the correct explanation of A
- A is true but R is false
The Correct Option is A
Solution and Explanation
When a bar magnet is dropped through a metallic cylindrical pipe, the phenomenon can be explained using Lenz's law and the induction of eddy currents:
- The changing magnetic flux due to the falling magnet induces eddy currents in the metallic pipe.
- According to Lenz’s law, these eddy currents generate their own magnetic field, which opposes the change in magnetic flux caused by the falling magnet.
- This opposing magnetic field creates an upward force on the magnet, reducing its acceleration and slowing its descent.
Comparison with a Non-Magnetic Bar:
A non-magnetic bar falling through the same pipe would not induce eddy currents because it does not have a magnetic field. The forces acting on the non-magnetic bar would be:
- Gravity, pulling it downward.
- Air resistance, which slightly opposes its motion.
Since there are no additional opposing forces (like those due to eddy currents), the non-magnetic bar falls more quickly than the magnet.
Analysis of Assertion and Reason:
- Assertion (A): The bar magnet takes longer to fall through the pipe than a non-magnetic bar of the same geometry and mass.
- Reason (R): Eddy currents in the metallic pipe create opposing magnetic fields, which slow down the descent of the magnet.
Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).
Final Answer:
Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).
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