Resistor Combinations Essay

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Experiment # 4 Title: Resistors in series and parallel. Objective: To investigate combinations of resistors. Equipment: Leads, DMM, Resistors, T – dec. IF YOU ARE NOT SURE ABOUT WHAT THE LECTURER HAS TOLD YOU TO DO, OR WHAT THE INSTRUCTIONS ARE, ASK !!!!!!!!!!!!!!!!!!!! DO NOT TRY TO DO SOMETHING YOU DO NOT KNOW HOW TO DO, OR SIT THERE IN SILENCE. Introduction. In the last experiment we combined resistors in series then in parallel. In the lab we will make up series / parallel combinations. Examples series / parallel combinations of resistors are shown below. While it would be unusual to actually purposely make up such combinations, they sometimes present themselves in electronic amplifier circuits, as equivalent circuits. Figure 1 Figure 1 http://www.ceb.cam.ac.uk/pages/series-parallel-circuits.html The link above analyses a number of combinations. We will only look at the one on the left above. Fir the values given, find the total resistance “seen” by the battery, V. Intuition will tell us that the total resistance “seen” by the battery will be greater than 80. Intuition will tell us that the total resistance “seen” by the battery will be greater than 80. We will start with the parallel combination of 100 and 50, to get a single resistor. The parallel combination of our two resistors reduces to Req = (R3 * R2) / (R3 + R2) = 100 * 50 / 150 = 33.3. The circuit is now a series combination of R1 + Req = 80 + 33.3 = 113.3. Method: 1. Measure the three resistors left out. Record their actual value from the meter, and their nominal value from the bands. Do not believe the lecturer or the box as to what the resistors are !! 2. From the calculations show above, determine the expected and nominal equivalent resistances. That is, use both the values

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