You have another capacitor w ith d ifferent

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Unformatted text preview: slow ly charge a capacito r, and then quickly releasing the capacitor’s stored electrical energy through a light bulb w hen a photo is taken. You think that the problem w ith your cam era m ay be that not enough energy is stored in the capacitor to properly light the flash bulb. You have another capacitor w ith d ifferent capacitance, but aren’t sure if you should connect it in series or in parallel w ith the original capacitor in order to store the m ost energy. You m ake an ed ucated guess, and d ecid e to test your prediction w ith circuits consisting of one or tw o initially uncharged capacitors, a battery, and a light bulb. You plan to m easure the am ount of tim e the bulb stays lit for one capacitor and for each of the possible arrangem ents of tw o capacitors, reasoning that if capacitors in a circuit can store m ore energy, they w ill take longer to fully charge. Instructions: Before lab, read the laboratory in its entirety as well as the required reading in the t extbook. In your lab notebook, respond to the warm up questions and derive a specific prediction for the outcome of the lab. During lab, compare your warm up responses and prediction in your group. Then, work through the exploration, measurement, analysis, and conclusion sections in sequence, keeping a record of your findings in your lab notebook. It is often useful to use Excel to perform data analysis, rather than doing it by hand. Read : Tipler & Mosca Chapter 24.2 & 24.3. EQUIPMEN T Build the circuits show n below out of w ires, resistors and light bulbs, capacitors w ith equal cap acitance, and batteries. You w ill also have a stopw atch and a d igital m ultim eter (DMM). Legend: light bulb battery capacitor C ircuit I C ircuit II Circuit III switch wire N ote: Check to make sure the light bulbs are all of the same type. To find identical bulbs look for markings on the base and check to see that the color of the bead separating the filament wires is the same. Read the section T he Digital M ultimeter (DM M ) in the Equipment a ppend ix. 71 CIRCUITS WITH TWO CAPACITORS – 1302Lab3Prob4 If equipme nt is missing or broken, submit a problem report by sending an email to l [email protected] . Include the room number and brief description of the p roblem. WARM UP 1. D raw a picture of each arrangem en t of the capacitors, light bulb, and battery. On each picture, label the capacitance of each capacitor. (Rem em ber that you w ill have capacitors w ith d ifferent capacitances.) Also, label the electric potential d ifference across each circuit elem ent and th e charge stored on the plates of each capacitor. 2. D ecid e on the p hysics principles you w ill u se. For a circuit, conservation of charge is usually u seful, as is conservation of energy. What is the relationship betw een the total energy stored in each circuit and the energy stored on each capacitor in that circuit? 3. For each capacitor, d eterm ine an equation that relates its stored energy, the charge collected on its plates, and its capacitance. 4. For each capacitor, w rite an equation relating the charge on its plates, the potential d ifference across the capacitor, and its capacitance. 5. A fter the current stops flowing t hrough the circuit, d o the tw o capacitors in Circuit II have the sam e am ount of stored charge? Circuit III? At that tim e, w hat is the potential d ifference across the bulb in each circuit? At that tim e, w hat is the relationship betw een the potential d ifference across the battery and the potential d ifference across each capacitor? 6. The target quantity is the energy stored in the capacit ors of each circuit. To d eterm ine w hich circu it stores m ore energy in the capacitors, you m ust calculate the energy stored in term s of quantities you can easily find , su ch as the potential d ifference across the battery and the capacitance of each capacito r. 7. From the previous steps, you can find the total energy stored in the capacitors in each circuit in term s of the potential d ifference across the battery and the capacitance of each capacitor. N ow com pare them to d eterm ine w hich is largest. Check your equations by making the comparison when both capacitors have the same capacitance. Does the result make sense? 8. W hat assum ptions m u st you m ake to relate the total energy stored in the capacitors for each configuration to the tim e the light bulb rem ain s lit after each circuit is closed ? PRED ICTION Restate the problem . What quantity do you w ish to com pare across the three situations? Use p hysics to d ecid e how they w ill com pare. Which quantity w ill you be 72 CIRCUITS WITH TWO CAPACITORS – 1302Lab3Prob4 m easuring d irectly? Describe qualitatively how it is connected to the quantity of interest. EXPLORATION WARN IN G: A charged capacitor can d ischarge quickly prod ucing a painfu l spark. D o not h and le the capacitors by their electrical term inals or connected w ires by their m etal end s. A lw ays discharge a capacitor before you use it and w hen you a...
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This document was uploaded on 02/23/2014 for the course MANAGMENT 2201 at University of Michigan.

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