In this worksheet, we will practice calculating the properties required for a superconductor to operate, referring to its critical temperature and critical field.

**Q2: **

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.

**Q3: **

Measurements of a superconductorβs 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.

(K) | 3.0 | 3.5 | 4.5 | 6.0 | 6.5 |
---|---|---|---|---|---|

(T) | 0.066 | 0.061 | 0.049 | 0.024 | 0.015 |

**Q4: **

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.

**Q5: **

Find the critical magnetic field of Mercury at 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.