77 78 lab 4 electric circuits in the first laboratory

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Unformatted text preview: esult in a maximum of 70% of the total points achieved) BONUS POINTS FOR TEAMWORK (as specified by course policy) * An "R" in the points column means to rewrite that section only and return it to your lab instructor within two days of the return of the report to you. 77 78 LAB 4: ELECTRIC CIRCUITS In the first laboratory, you stud ied the behavior of electric field s and their effect on the m otion of electrons using a cathod e ray tube (CRT). This beam of electrons is one exam ple of an electric current – charges in m otion. The current in the CRT w as sim ple in that the electrons m oved through a vacuum . The forces on them w ere com p letely know n. Their behavior could be d eterm ined by calculating the electric field and then applying kinem atics. In contrast to the CRT, com m on electric currents are insid e m aterials such as w ires or light bulbs. Even though the interactions of electrons insid e m aterials are quite com plicated , the basic principles of physics still apply. Conservation of energy and charge allow us to d eterm ine the overall behavior of elect ric currents w ithout the need to know the d etails of the electrons’ interactions. This approach to problem solving in the realm of electric circuits w ill give you m ore experience in applying the very useful principles of conservation. O BJECTIVES A fter successfully com pleting this laboratory, you should be able to: A pply the concepts of circuits to electrical system s. A pply the concept of conservation of charge to d eterm ine the behavior of the electrical current through any part of a circuit. A pply the concept of conservation of energy to d eterm ine the behavior of the energy output of any elem ent in a circuit. U se the concept of electric potential to d escribe the behavior of a circuit. Relate the electric charge on a circuit elem ent to the potential d iffer ence across that elem ent and the capacitance of that elem ent. Relate the electric current through a circuit elem ent to the resistance of that elem ent and potential d ifference across that elem ent. M easure the current through a circuit elem ent w ith a d igital m ultim eter (DMM). M easure the voltage betw een tw o points in a circuit w ith a DMM. M easure the resistance of a circuit elem ent w ith a DMM. PREPARATION Read Tipler & Mosca: Chapter 23 section 1; Chapter 24, sections 1, 2, 3; Chapter 25. It is likely that you w ill be d oing these laboratory problem s before your lecturer ad d resses this m aterial. The purpose of this laboratory is to give you these experiences as an 79 LAB 4: ELECTRIC CIRCUITS introd uction to the m aterial. So, it is very im portant that, w hen you read the text before com ing to lab, you remem ber the objectives of the laboratory. Before com ing to lab you should be able to: D escribe the relationship betw een charge and current. D escribe the relationship betw een potential and potential energy. D escribe the essential d ifferen ce betw een an insulator and a cond uctor. Id entify w hat is an electrical circuit and w hat is not. A pply conservation of energy and conservation of charge to current flow ing around a circuit. W rite d ow n Ohm 's law and know w hen to apply it. D escribe the d ifference betw een a capacitor, a resistor, and a battery. U se a DMM to m easure potential d ifference, current, and resistance. 80 PROBLEM #1: SIMPLE CIRCUITS You need more light in your workroom, so you decide to add another light fixture to your track lighting. However, you are concerned that adding another light may dim the lights that are already in the track. When you proceed with the addition of another light, you notice that none of the lights are dimmer than before. You wonder what type of circuit your track lighting uses. You decide to build models of circuits with two bulbs connected across a battery, and to compare the brightness of the bulbs in these circuits to a reference circuit with a single bulb. The circuit in which each bulb is as bright as the one in your reference circuit is the same type as the circuit in your track lighting. Instructions: Before lab, read the laboratory in its entirety as well as the required reading in the textbook. 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. EQUIPMENT You will build three simple circuits shown below out of wires, bulbs, and batteries. Use the accompanying legend to build the circuits. Legend: light bulb battery wire Note: 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. If equipmen...
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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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