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Worksheet: Superconductors

Q1:

At what temperature, in terms of the critical temperature 𝑇 𝑐 , is the critical field of a superconductor one-half its value at 𝑇 = 0 K ?

  • A 1 𝑇 𝑐
  • B 0 . 5 𝑇 𝑐
  • C 1 . 5 𝑇 𝑐
  • D 0 . 7 0 7 𝑇 𝑐
  • E 2 𝑇 𝑐

Q2:

Measurements of a superconductor’s critical magnetic field at various temperatures are shown in the accompanying table. Determine the value of the critical magnetic field at absolute zero. Assume a critical temperature value of 7.2 K.

𝑇 (K) 3.0 3.5 4.5 6.0 6.5
𝐡 𝑐 (T) 0.066 0.061 0.049 0.024 0.015

Q3:

A tightly wound solenoid at a temperature of 4.2 K is 60 cm long and is constructed from a Pb wire of radius 1.6 mm. Find the maximum current that the solenoid can carry at which the wire remains superconducting. Use a value of 7.2 K for the critical temperature and use a value of 0.080 T for the value of the critical magnetic field at absolute zero.

Q4:

Find the critical magnetic field of Mercury at 𝑇 = 2.6 K. Use a value of 4.2 K for the critical temperature and use a value of 0.041 T for the value of the critical magnetic field at absolute zero.

Q5:

A Pb wire wound in a tight solenoid of diameter of 4.0 mm is cooled to a temperature of 5.0 K. The wire is connected in series with a 50-Ξ© resistor and a variable source of emf. As the emf is increased, what value does it have when the superconductivity of the wire is destroyed? The critical temperature of Pb is 7.2 K and the critical field value for Pb is 0.080 T.