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Lecture Demonstrations Laboratory

Physics Rm. 202

(434) 924-6800


The Demonstrations Manual


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Electrostatics
Electric Fields And Potential
Capacitance
Current and Resistance
Resistance Model
Temperature Effects on the Resistance of Copper Wire
Temperature Effects on Resistivity
Superconducting Wire
Electromotive Force And Current
DC Circuits
Magnetic Materials
Magnetism
Inductance
Induction
Complex Circuits
Semiconductors And Tubes
Transmission Lines and Antennas

Superconducting Wire

Purpose:

Show the resistance of a superconductor vanishes below the critical temperature. Tc = 90K for YBCO.

Procedure:

This demo utilizes a short length of high temperature superconducting (HTS) wire, which is actually shaped like a ribbon with Yttrium Barium Copper Oxide (YBCO) sandwiched between two layers of stainless steel. Tc = 90K. For example, STI describes some of the different superconducting wires.

Connect power supply to black and red leads. Connect the other two leads to the microvoltmeter.

Turn ON the power supply and adjust the current until 1/2 A flows through the wire. The room temperature voltage will measure just under 2mV.

Have students watch the reading on the voltmeter while the LN2 is poured into the Styrofoam container. After a few seconds, the voltage drop across the wire will fall to zero.

Hints:

Must use a power supply that can control current:
  • Keithley 2231-30-3 Triple Channel DC Power Supply
  • HP 6214A DC Power Supply
Must use a voltmeter that can measure down to 1μV:
  • Keithley 177 Microvoltmeter

Equipment:

  • Digital Multimeter
  • Superconducting wire apparatus