W101BLLab050

# W101BLLab050 - Physics 1B BATTERIES AND CAPACITORS Winter...

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Physics 1B B ATTERIES AND C APACITORS Winter 2010 Page 1 Introduction In this lab you will explore ideas about electric circuits using batteries, wires, a light bulb, and one or more capacitors. Read all the steps in each part before you start. Pre-Lab Read sections 16.1 - 16.9 in “College Physics” by Serway & Faughn. 1. Three 1.5 μ F capacitors are wired together in-series, and then these three are connected in- parallel with a 2.5 μ F capacitor. What is the equivalent capacitance of this arrangement of capacitors? 2. You have two capacitors, one is 2.5 μ F the other is 5.0 μ F. You also have some wires and a 9.0 V battery. a. Using the schematic symbols on page 2, draw a diagram of a circuit with the two capacitors connected in series with the battery. Draw a diagram of a circuit using the same battery and capacitors with the capacitors connected in parallel. Find the equivalent capacitance for each circuit. b. For each of the two circuits drawn in part (a) determine the charges on each capacitor. c. For each of the circuits from part (a) determine the total energy stored by the capacitors. Which configuration stores the greater amount of energy? Which configuration stores the greater amount of charge? 3. Suppose a parallel plate capacitor (with capacitance C 1 ) is fully charged (to a value Q o ) by a battery. The battery (which supplies a potential difference of V o ) is then disconnected. If the plates of the capacitor are then moved closer together (the separation distance d between the plates is halved), describe quantitatively what happens to: a. the capacitance of the capacitor. b. the potential difference between the plates. c. the energy stored in the capacitor. d. the charge on the plates. A. Group Activity A1 . Suppose you are given a battery, a capacitor, two switches, a light bulb and several pieces of connecting wire. Design a single circuit that will do both of the following: (a) When switch 1 is closed and switch 2 is open, the capacitor charges but no current moves through the light bulb, and (b) when switch 1 is open and switch 2 is closed, the light bulb is connected to the capacitor but not the battery. Draw your circuit on the white board and get your TA to check it before you go on to the next section. A2. Suppose you set up this circuit with both switches open and no charge on the capacitor. Describe the motion of charge in the circuit when you close switch 1 (leaving switch 2

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Physics 1B B ATTERIES AND C APACITORS Winter 2010 Page 2 open). Is energy being stored on the capacitor? What measurements could you make to discover how much energy is stored, if any? What (if anything) happens to the light bulb? A3. After switch 1 has been closed for a while, you open it. Then you close switch 2. What will happen to the light bulb now? What happens to it as time passes? What happens to the capacitor? How could you confirm your predictions? A4.
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## W101BLLab050 - Physics 1B BATTERIES AND CAPACITORS Winter...

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