PHY 2049L
Lab 8

RC and LCR Circuits (AC)

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Updated: 2/2/2013
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Guiding Question:

IMPORTANT:
You must bring an extra copy of the cover page for your Lab 6 report so you can use the abstract from that report and also include it in "worksheet" section of your Lab 7 report. You will need the information in your abstract to identify which "thin" box is to be used for your measurements this week and to get the values of L and r needed for the calculations. It should go without saying that both your Lab 6 and Lab 7 abstracts need to clearly identify which "thin box" you used.

Preparing for the lab:

Be sure you have an extra copy of your Lab 6 abstract!

We will be doing "Lab 37" pretty much as described in the lab manual except for the specific values of the resistors being used.

Answer the pre-lab questions on LON-CAPA after reading the background information on pages 369 through 371 in the lab manual.

When reviewing the lab procedure before class, make a note of the changes we will make in the values used (see below). The combination was chosen so the resonant frequency of the circuit is close to one of the frequencies used, just as is the case in the circuit described in the manual.

Comment

We will be using the same inductor (nominally about 80 mH and 200+ ohm, located between the 13-14 connectors in the "thin" box) as in the LR experiment. The capacitor we will use is also in the "thin" box, located at the 21-22 connectors. It has a nominal value of about 0.5 mu F. (This is not the capacitor used for the RC circuit experiment.)

In Part One of the experiment we will use a frequency of 250 Hz and four resistors in the "thick" box (995, 680, 470, and 330 ohm). This procedure for determining C is similar to what was done to determine L in last week's lab. In Part Two we will use the 330 ohm (7-8) and 220 ohm (9-10) resistors at two frequencies (600 and 800 Hz). Note that it is easier if you make both resistance measurements for a given frequency and then change to the other frequency. The order described in the manual requires setting the frequency (which is sometimes difficult) four separate times.


Apparatus

As was the case for the LR lab, this picture does not show the actual set of cables you will have. See below for details on the cables that are available. I again suggest using the longest (100 cm) cables as measurement leads connected to the multimeter (in AC volts mode), the 65 cm cables to connect the wave generator to the circuit, and the shorter cables to make up the rest of the circuit.

sine wave generator and frequency counter, plus R and LC boxes

As you can see, the equipment for this experiment is essentially the same (sine wave generator, frequency counter, "thick" R box, "thin" LC box, cables) as used for the LR experiment. The only difference is that we will need one more short cable than we needed in the previous lab.


Cables

The set of cables shown in the picture below contains the ones you will have available for this lab. The set above the meter stick includes a red-black pair of 100 cm leads and a red-black pair of 65 cm leads. One of these pairs is usually used to make connections to the multimeter while the other is used to connect to the power supply.

Full set of 9 cables used in circuit labs

The set below the meter stick includes a red-black pair of 40 cm leads, an extra 40 cm lead that is black with red connectors, and a red-black pair of 20 cm leads. The shortest cables are used for connections between nearby points on a resistor box.

 
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