AIIMS 2007 Physics Properties of Superconductors Assertion Reason Question

To analyze the given assertion and reason, let's break down the concepts involved:

Assertion:

A current continues to flow in a superconducting coil even after the switch is off.

Reason:

Superconducting coils show the Meissner effect.

Evaluation of Assertion:

The assertion is true. Superconductors exhibit a phenomenon known as persistent current. When a superconducting coil is initially energized, it allows an electric current to flow without resistance. Once the current is established and the switch is turned off, the superconducting state allows the current to continue flowing indefinitely due to the lack of electrical resistance. This is a key characteristic of superconductors.

Evaluation of Reason:

The reason is also true. The Meissner effect is a property of superconductors that causes them to expel magnetic fields from their interior when they transition into the superconducting state. This expulsion means that the magnetic field lines cannot penetrate the superconductor, which helps maintain the persistent current as the system does not lose energy to resistive heating.

Relationship Between Assertion and Reason:

While both statements are true, the reason provided does not directly explain the assertion. The persistent current in superconductors is primarily due to the absence of electrical resistance rather than the Meissner effect. The Meissner effect is more about magnetic field behavior in superconductors, while the assertion emphasizes the flow of electric current.

Conclusion:

Since both the assertion and the reason are true, but the reason does not serve as the correct explanation for the assertion, the correct option is: B) If both assertion and reason are true but reason is not the correct explanation of assertion.

Clarification of Other Options:

• Option A: This would be correct only if the reason provided were the correct explanation for the assertion. However, since the reason does not explain why the persistent current occurs, this option is incorrect.
• Option C: This option states that the assertion is true but the reason is false. Since both statements are true, this option is incorrect.
• Option D: This option states that both the assertion and the reason are false. Since both are true, this option is also incorrect.

Relevant Concepts:

1. Superconductivity: A state of matter where materials exhibit zero electrical resistance and expel magnetic fields below a critical temperature.
2. Meissner Effect: The phenomenon where a superconductor expels all magnetic fields from its interior, which is significant for maintaining superconducting properties but does not explain persistent current.

Summary:

In summary, the correct answer is B because both the assertion and reason are true, but the reason does not correctly explain the phenomenon of persistent current in superconductors.