MCQ Detailed View

The correct answer is Adiabatic demagnetization. This principle is used in physics to produce extremely low temperatures, often approaching fractions of a degree above absolute zero. Adiabatic demagnetization is an essential technique in cryogenics, where low temperatures are needed for scientific experiments, superconductivity studies, and quantum research.

The principle works based on magnetic cooling. A paramagnetic material, such as a salt with unpaired electrons, is first placed in a strong magnetic field. The magnetic moments of the atoms align with the field, reducing their entropy. Then, the system is thermally isolated (adiabatic condition), and the magnetic field is gradually reduced. As the field decreases, the magnetic dipoles become more disordered, absorbing energy from the thermal motion of the atoms, which results in cooling of the material.

This method can achieve temperatures as low as millikelvin, far lower than can be reached by conventional methods like the Joule-Kelvin effect, which is used for gas expansion cooling, or the thermo-electric effect, which produces small temperature differences using electric currents. Superconductivity, while occurring at low temperatures, is not a method to produce low temperatures itself; it is a property that appears once the material is sufficiently cooled.

Adiabatic demagnetization is widely used in experimental physics, low-temperature chemistry, and solid-state research to study phenomena like quantum behavior, magnetic ordering, and superconductivity under extremely low thermal conditions.

🔑 Key Facts:

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  Adiabatic demagnetization = technique to achieve very low temperatures.

  
  


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  Works with paramagnetic materials and strong magnetic fields.

  
  


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  Cooling occurs due to increase in entropy when the field is reduced.

  
  


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  Can reach millikelvin temperatures, near absolute zero.

  
  


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  Used in cryogenics, quantum research, and superconductivity studies.

  
  

👉 Final Answer: The principle used to produce low temperatures is Adiabatic demagnetization.