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Lecture Demonstrations Laboratory


The Demonstrations Manual


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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
Series LCR Circuit, Resonance
Coupled Electrical Oscillators
Semiconductors And Tubes
Transmission Lines and Antennas

Series LCR Circuit, Resonance

Purpose:

To show phase response in a LCR circuit and behavior of current at resonance.

Procedure:

Connect 0.47uF capacitor, 4.25mH air core coil and a 2V bulb (resistor) in series as shown in the pictures below. Use the PASCO generator's sine waves as a signal source. Vary the frequency of the generator to observe the resonance at about 3.5KHz (the bulb will light bright). Vary any of the system parameters (R,C, or L as in RC and LR demos) to observe the change in the resonance frequency. By simultaneously measuring the voltage across the inductance and the capacitance one will observe that at resonance these voltages are the same and 90deg out of phase. Also at frequencies above the resonance the circuit becomes inductive (the voltage drop across C goes to zero) and at lower frequencies the circuit becomes capacitance driven.

Hints:

Do not connect anything to the oscilloscope ground. The scope should have a different input.

Comments:

If you have a suggestion for the use of this demo which might benefit others, you can enter it below.

Equipment:

  • Oscilloscope
  • Large Bread Board
  • Inductor
  • Connecting Wires
  • Capacitor
  • Resistor