If vacc is 300v vx 8v and vy 3v w hat is the d

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Unformatted text preview: b, assu m e that the d istance from the center of the Vx plate to the fluorescent screen is 10 cm and the d istance from the center of the Vy plate to the screen is 8 cm . If Vacc is 300V, Vx = -8V and Vy = 3V, w hat is the d isplacem ent of the electron beam ? 3. A ssum e you have tw o infinite parallel planes of charge separated by a d istance d as show n below . Use the sym bols <,>, and = to com pare the force on a test charge, q, at points A, B, and C. + + + + + - - A B C - - - 31 CHECK YOUR UN D ERSTAN D IN G LAB 1: ELECTRIC FIELD S AN D FORCES 32 TA Name: PHYSICS 1302 LABORATORY REPORT LAB 1: Name and ID#: Date performed: Day/Time section meets: Lab Partners' Names: Problem # and Title: Lab Instructor's Initials: Grading Checklist Points LABORATORY JOURNAL: PREDICTIONS (individual predictions and warm-up completed in journal before each lab session) LAB PROCEDURE (measurement plan recorded in journal, tables and graphs made in journal as data is collected, observations written in journal) PROBLEM REPORT:* ORGANIZATION (clear and readable; logical progression from problem statement through conclusions; pictures provided where necessary; correct grammar and spelling; section headings provided; physics stated correctly) DATA AND DATA TABLES (clear and readable; units and assigned uncertainties clearly stated) RESULTS (results clearly indicated; correct, logical, and well-organized calculations with uncertainties indicated; scales, labels and uncertainties on graphs; physics stated correctly) CONCLUSIONS (comparison to prediction & theory discussed with physics stated correctly ; possible sources of uncertainties identified; attention called to experimental problems) TOTAL(incorrect or missing statement of physics will result in a maximum of 60% of the total points achieved; incorrect grammar or spelling will result 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. 33 34 LAB 2: ELECTRIC FIELD S AN D ELECTRIC POTEN TIALS In this lab you w ill continue to investigate the abstract concept of electric field . If you know the electric field at a point in space, you can easily d eterm ine the force exerted on a charged object placed at that point. The concept of field has the practical ad vantage that you can d eterm ine the forces on an object in tw o stages. To d eterm ine the force exerted on object A by other objects, you first d eterm ine the field , at a location to be occupied by A, due to all objects except for object A . You then calculate the force exerted on object A by that field . That force d epend s only on t he properties of object A a nd t he value of the field a t object A’s location. An ad vantage of this tw o-step approach is that if you m ake no changes but replace object A w it h a new object, B, it is sim ple to calculate the force exerted on object B. This is because replacing A w ith B d oes not change the field . T he field that exerts a force on an object depends only on the other objects. Keeping track of forces and accelerations is not alw ays the simplest approach for pred icting the behavior of objects. It is often m ore convenient to use the principle of Conservation of Energy. As m entioned in the introd uction to the previous lab, the potential energy related to the position of a charged object resid es in the surround ing field . As w ith forces on an object (A) d ue to a field , the change in potential energy d ue to the ad d ition of an object (A) to a configuration of other objects is calculated in tw o stages. First you calculate the “potential,” at a location to be occupied by object A, due to all objects except for object A . That potential d epend s only on the other objects and d oes not d epend on any properties of object A. You then use the value of the potential at that location to calculate the change in potential energy w hen object A is placed there. That potential energy d epend s only o n the properties of object A and the value of the potential at object A’s location. As w ith forces, it w ould then be a sim ple m atter to calcu late the potential energy change d ue to replacing object A w ith another object B. Because the concepts of field and potential are abstract and d ifficult to visualize, this laboratory uses a com puter sim ulation based on the interaction of point charged objects (usually called point charges). With this sim ulation you can construct a com plicated charge configuration and read out the resulting electric field and electric potential at any point in space. O BJECTIVES A fter successfully com pleting this laboratory, you should be able to: Q ualitatively d eterm ine the electric field at a point in space caused by a configuration of charged objects based on the geom etry of those objects. C alculate the electric field at a point in space caused by a configuration of cha rged objects based on the geom etry of those objects. 35 LAB 2: ELECTRIC FIELD S AN D ELECTRIC...
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