W101BLLab06-1 - Physics 1BL CURRENT AND RESISTANCE Winter...

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Physics 1BL C URRENT AND R ESISTANCE Winter 2010 Page 1 Introduction In this lab we will examine the concepts of electric current and potential in a circuit. We first look at devices (like batteries) that are used to generate electrical energy that we can use in circuits. Then we consider how the current through certain circuit elements depends on the voltage across them. Finally we show how the electrocardiogram can give information about electrical activity inside the human heart. You should review chapter 17 of Serway and Faughn before coming to lab. Pre-lab questions: 1. You have a circuit consisting of six 1.5 V D-cell batteries in series, some wires, and a light bulb. The bulb is lit and the current flowing through the bulb is 0.50 A. You may assume that all of the voltage drop occurs in the light bulb. What is the resistance of the bulb? 2. a) Which direction (clockwise or counterclockwise) does an electron travel through the wire in the figure to the right? Explain. b) At which point ( a or b ) will an electron have more electric potential energy? Explain. c) At which point ( a or b ) will an electron have more electric potential? Explain. 3. The power rating on a light bulb indicates how much power it would dissipate when it is hooked up to the standard household voltage of 120 V (this rating does not mean that the light bulb always dissipates the same amount of power, assume that the resistance is constant in this case). (a) How much power is dissipated in a light bulb that is normally rated at 60 W, if instead we hook it up to a potential difference of 60 V? (b) How much power is dissipated in a light bulb that is normally rated at 60 W, if instead we hook it up to a potential difference of 240 V? A. Group Activity: After your group has answered each of these questions, call your TA over to discuss them. A1 . Your TA gives you a capacitor and tells you it is charged. How can you determine if this the capacitor really is charged? What equipment would you need and what measurements would you need to make? A2 . Now suppose you connect a wire between the two terminals of the charged capacitor. Does the charge in the wire flow (a) from the positive plate to the negative plate, (b) from the negative plate to the positive plate, or (c) both of these? Have you done any experiments in this lab to demonstrate this? Figure 1
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Physics 1BL C URRENT AND R ESISTANCE Winter 2010 Page 2 A3 . Describe a situation in which both positive and negative charge carriers are responsible for an electrical current. A4 . Suppose you connect one plate of a charged capacitor to one terminal of a light bulb. Then connect the other terminal of the bulb to the other capacitor plate. Figure 1 shows the circuit. Compare the charge flow at points a and b on each side of the light bulb?
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W101BLLab06-1 - Physics 1BL CURRENT AND RESISTANCE Winter...

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