PHY 2049L
Lab 3

Basic Circuits

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Updated: 1/21/2013

Guiding Questions:

Preparing for this lab:

This is a completely new lab directed at discovering the rules that govern the voltages and currents in different kinds of simple circuits, so there is no information in the lab manual that is specifically about this experiment.

Review the information about adding resistors in "Lab 28" (the Ohm's Law experiment) in addition to what is in our lecture textbook before answering the pre-lab questions on LON-CAPA.

You should also review the instruction sheets from Lab Zero and the information in Fig. 25.17 (page 429 of Wolfson) and Fig. 25.14 (page 428) about using meters before answering the last question on LON-CAPA. Pay particular attention to the "TIP" on page 429 of Wolfson. (Page and figure numbers are for the second edition.)


The main challenge here is getting things wired up correctly to reproduce the circuit diagrams you are given. I will give the specifics for what connects to what with a handout in the lab (the same info is on a separate procedure page),

(Note that each setup has slightly different resistors, so you will need to do the final calculations for the lab report with the specific values from the resistor box at your lab station.


Cenco power supply, resistor box, plus familiar items from last lab

The resistors we will use are arranged in the left-hand column of the wooden resistor box. Be sure to record which box you used so you can include it in your abstract!

We will use the BK Precision multimeter much like we did in the previous lab. We will use it as a voltmeter (same button settings as shown in photos for an earlier lab) to set and spot-check the voltage from the Kenwood power supply and to measure the voltage across each circuit element. We will use the Keithley meter as a DC ammeter. Remember to select the 2000 mA range and only connect the cables to measure a current AFTER having your plan checked by the lab instructor. At that point you can change the range setting to get the maximum number of sig figs for the largest current we expect to measure. Do not change the range between measurements for the same part of the experiment.


The set of cables shown in the picture above is the full set available for any particular electrical circuit lab. You will not need all of them for this lab, but they will all be available so you can choose the ones you want. 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.


The procedure is explained in detail on a separate handout. This lab is not described at all in the lab manual.


 ?? Contact me if you have any questions.