Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538

# Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography

Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.

 Choose a Topic or Enter a keyword to search: I cannot find what I want! You have selected the following Demos: None Selected

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

### video  - Superconducting Wire

#### Purpose:

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

#### Procedure:

DEMO VIDEO DOWNLOAD w/ sound / 1920x1080 / 24.19Mb/s / 231MB size

DEMO VIDEO DOWNLOAD w/ sound / 854x480 / 5.69Mb/s / 55MB size

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:
• Keysight 34461A Digital Multimeter
• Keithley 177 Microvoltmeter

#### Equipment:

• Digital Multimeter
• Superconducting wire apparatus