Al Tobias (wat4y) - Office: Rm. 201, (434) 924-0538 - Lab: Rm. 202, (434) 924-6800

# 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:
(Clicking a green button will add that demo to your list)
Electrostatics
Electric Fields And Potential
Capacitance
Current and Resistance
Electromotive Force And Current
DC Circuits
Magnetic Materials
Magnetism
Inductance
Induction
Complex Circuits
Parallel LCR Circuit or Tank Circuit
video  - Series LCR Circuit, Resonance
Coupled Electrical Oscillators
Semiconductors And Tubes
Transmission Lines and Antennas

### Parallel LCR Circuit or Tank Circuit

#### Purpose:

To demonstrate inductive and capacitive reactance, resonance, and response of an LC tank circuit.

#### Procedure:

Use the R or C switch position on the substitution box and connect the circuit. Connect the scope to the points indicated and ground it to the function generator. The generator acts like a current source to drive the tank circuit so at resonance the current (Ch. A) will be in phase with the voltage across the tank circuit (Ch. B). Slightly below resonance, the tank circuit behaves inductively and the voltage will lead the current. Slightly above resonance, the circuit behaves capacitively and the voltage will lag the current. Also, at resonance, since the impedance of the tank circuit is infinite (ideally, assuming no losses, etc.), maximum signal voltage will be seen. The Q for this circuit is fairly good so a nice peak around resonance can be seen. Resonance for the above circuit occurs at about 7.8 kHz. A schematic for the setup is shown below.

#### Hints:

Use 4.5 mH copper coil inductor

#### Equipment:

• Oscilloscope
• HP sine wave generator
• Resistor - Capacitor Substitution Box
• Inductor