# Physics 109 - Resonant Circuits Part I

Today's lab starts with another invention activity. A data set for working with the inventiona activity can be found HERE.

Once you have completed the invention activity we will have a short lesson. if you are done before the lesson, start assembling the circuit below.
After the lesson, you will use last week's data to do an unweighted fit AND an esyimated unsertainty in the slope

A resonant circuit:
One of the most common models for physical systems is the harmonic oscillator. A classic example is mass on a spring. When you give the mass a sudden push it oscillates at some natural frequency and those oscillations gradually die away until the next push. Today you will study an electronic version of this - the series combination of an inductor, a resistor and a capacitor (LRC). After your instructor has outlined how to build this circuit, go ahead and assemble one yourself. The 'kick' you will be giving to the circuit comes by driving it with square waves from your function generator, set to about 100 Hz. You'll see the response of the circuit on your oscilloscope.

• Draw a diagram of a series LRC circuit
• Assemble the circuit
• Set the function generator to 100 Hz square waves
• use a resistance of 5 Ohms
• use a capacitance of 0.04 microFarads
• You can trigger the oscilloscope externally by connecting the 'SYNC' output of the function generator to the 'EXT TRIG' connection on your oscilloscope

Measure the amplitude of the oscillations as a function of time, all the way to the point at which the oscillations have disappeared into the electrical noise (do not use the averaging mode of the oscilloscope, since we want you to see the impact that noise has on your measurments and data analysis).

Marking Scheme

participation in invention activity: 2 marks

Graph and unweighted fit to last week's data, including uncertainty in the slope: 3 marks

comparison of slope and uncertainty to the expected value of the capaciatance: 1 mark

LRC data taking:

circuit diagram, description of data-taking method, and justification of uncertainty estimates: 3 marks
linearized plot of amplitude versus time: 3 marks