Record the values and the colors in Data Table 1. Determine the resistance of each resistor, using the Resistor Color Code Chart on page 17. Measure the resistance of each resistor individually using the ohmmeter (i.e., the multimeter). As in the case for series we can generalize this law to any number of resistors: 11 1 1 1 R R RR FIR + + + + eq N 00673402-1 So, Req=14812 We can generalize this equation to any number of resistors, just the way we did for resistors in series. You have to flip that over in order to get Req! Here's an example: If we have R1 = 27022 and R2 = 33082 we would find Req as follows: + Instead of the resistances adding directly, we calculate 1 1 1 Req R1 R2 It's important to remember that after you do this calculation, you will have gotten 1/Req. In this case, the equation is a bit more complicated than for resistors in series. In lecture, we used this property of resistors in parallel to derive an equation for calculating the equivalent resistance. Resistors in parallel "see" different currents, but they each experience the same potential difference (voltage). Therefore, they see” different amounts of current, just the way water branching into two different pipes will flow more through the larger pipe (lower resistance) than through the narrower pipe (greater resistance). When resistors are in parallel, the current flowing from the battery will come to a junction where it has a "choice" as to which branch to take. In series they were connected one after the other, but in parallel, as the name suggests, they are 'side by side' in the circuit. We say these resistors are connected in parallel. In the second part of this lab we'll hook them together as in Figure 2. You (hopefully!) remember from lecture this isn't the only way to hook up resistors in a circuit. V ERI ZR2 Figure 2: Two resistors in parallel Req = R, + R2 + R2 +. In lecture, we showed that the equivalent resistance for resistors in series is Req = R + R2 Of course, this equation can be extend to any number of resistors in series, so that for N resistors the equivalent resistance is given by Req=ER (for i=1,2,3.,N) connected in series and you send water through them, each receives the same amount of water, there are no branches into which the water can split. Recall the water analogy: If you have two pipes that have different diameters but are RI V ER eq ER2 (a) The actual circuit (b) The equivalent circuit Figure 1. Remember from lecture that, when resistors are connected in series, each one "sees" the same current.
Figure 1 shows two resistors connected in series (a) and the equivalent circuit with the two resistors replaced by an equivalent single resistor (b), as we discussed in the lecture. Transcribed image text: Theory: In the first part of this experiment we will study the properties of resistors, which are connected "in series”.
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