Subject: Physics    / General Physics


Physics 8E Volume 2 -Cutenll and Johnson (2009) (”>

ISBN: 978-0-470-37925-7

Lab 1 Introduction

Lab 1 – Coulomb’s Law

Lab 1 (Chapter 18, Lesson 3 and Concepts & Calculations Example 17 on page 563) involves the vector nature of electric forces.

In this simulation, the green, red, and blue charges are originally (i.e., at t = 0) at the vertices of an isosceles triangle. The green and blue are fixed in space and the red charge is allowed to move.

Find the net Coulomb force (magnitude and direction) on the red object due to the green and blue charged objects after 1.00 s has elapsed. This simulation file name is “Net Coulomb Force”.

Fill in the blanks in the Lab Answer Sheet at the end of this lab.

You use the data from the “Time” and “Position” measurement tables (red, green, and blue) to help in calculating individual electrostatic (Coulomb) forces and directions. Finally, calculate the net Coulomb force, Fc and direction, on the red object after 1.00 s.

Lab 2 Introduction

Lab 2 – Mapping E field Lines

Lab 2 (Chapter 18, Lesson 3) involves mapping of E lines for a certain unknown charge distribution. You will be mapping electrostatic (Coulomb) force lines since the electric field E is proportional to the Coulomb force by the equation (Equation 18.2) but these are equivalent to the E lines with equivalent directions and proportional magnitudes. This simulation file name is “EXP #3 E FIELD #3”

The direction of the electric field (or Coulomb force – Total Force in this experiment) is determined by placing a small + test charge, green in color throughout these simulations, near a charged configuration and noting the direction that the test charged is accelerated. You are free to move the small green test charge around to various locations, while noting (1) the exact location and (2) the direction of the force on that charge caused by all other charges.

On graph paper (on your answer sheet), record the E field direction at the appropriate locations for the green test charge. Try to connect the arrows in a line to form the electric field lines. These lines may not cross each other. For test charge locations, choose the corners of the squares all around the charged object(s).

Lab 3 Introduction

Lab 3 – Charged Object Moving in a Capacitor

Lab 3 (Chapter 18, Lesson 3 and Sections 18.6 and 18.7) involves the vector characteristics of a moving charged object within a charged parallel plate capacitor. This simulation file name is “#15 Charge and Cap”. A positively charged particle is moving horizontally when it enters the region between the plates of a capacitor as the simulation illustrates. (a)

Draw (sketch) the trajectory that the particle follows in moving through the capacitor. (b) When the particle is within the capacitor, which of the following four vectors, if any are parallel (||) to the electric field E inside the capacitor: the particle’s displacement (), its velocity (v), its linear momentum (p), and its acceleration (a)? For each vector, explain why the vector is or is not parallel to the electric field of the capacitor.

Run simulation noting the particle’s trajectory (as indicated by the “tracking” or “strobes”) while inside the capacitor cavity. Also note the velocity and acceleration vector, v and A, respectively arrows.

Fill in the answers for the blanks in the Lab Answer Sheet at the end of this lab.

A capacitor is a charge storage device. A parallel plate capacitor consists of parallel conducting plates separated by an insulator. In this experiment, the insulator is air and there is equal but opposite charges (+Q and –Q) placed on each conducting plate (See Figure 18.25, Section 18.6 and 18.7 in your textbook). This virtual lab investigates the effects (if any) of a positively charged particle midway between the oppositely charged plates of a parallel plate capacitor moving in a + x-direction. Just as in Lab 3, there will exist an electrostatic (Coulomb) force on the charged particle when it is inside the capacitor.

In this lab, you will investigate electric field (E) lines. Electric charges create an electric field in space surrounding them. Electric field lines essentially give us a “map” of the direction and strength (magnitude) of the E field at various places in space. E lines are always directed away from positive charges and toward negative charges (see Figure 18.23, textbook Section 18.7, and Lesson 3). In Figure 18.27 the absence of E lines indicates that the electric field is relatively weak between the two positive charges. Since you will be performing in this experiment a virtual mapping of E lines for a certain charge distribution, carefully study Conceptual Example 13 (“Drawing Electric Field Lines”) for the dos and don’ts of mapping E field lines.

Electric Field Lines Mapping Rules

-The E lines do not cross each other

-The closer the lines are together, the stronger the E in that region

-The field lines indicate the direction of E; the field points in the direction tangent to the field line at any point

-The lines are drawn so that the magnitude of the electric field, |E|, is proportional to the number of lines crossing unit area perpendicular to the lines. The closer the lines, the stronger the field

-E lines start on + charges and end on – charges; the number starting or ending is proportional to the magnitude of the charge.



At successful completion of this lesson, you will be able to:

·Use Interactive Physics “IP” to conduct virtual physics experiments.

·Use IP to acquire data for analysis of wave characteristics.

·Use IP to gain a better understanding of electrostatic Coulomb forces.

·Use IP to map electric field (E) lines for a charge distribution.

·Use IP to conceptually investigate a charged particle moving between the parallel plates of a charged capacitor.

Write up a lab report for each of the three experiments.

Use the report sheet to present data in the report and answer questions.

From your observations and data, write a report about the experiment by completing tables, making graphs, and answering questions. All tables are to be done on a spreadsheet, and all graphs are computer generated.

Title Page: Must be in MLA format and center: Title of the lab, the experiment number.

Introduction: Describe objectives and concepts of lab. Define any key words, show any equation you use in the lab, and describe any theory or law that is used. DO NOT describe the procedures of the experiment or copy the objectives from the handout. The introduction should be no shorter than 1/2 page in length.

Procedure: Only use if modification or changes are made in the experiment. If this is the case, you will need to describe how the experiment was modified.

Data: The measurements and observations you make must be recorded in neatly prepared data tables.

Results and sample calculations:Raw data collected is to be manipulated in this section. This normally involves calculating quantities using relevant equations. When calculating a quantity, the calculation must be shown step by step. This is to indicate that you are performing the correct procedure.

Further calculation of the same quantity need to be shown only if requires the use of a different equation. For example, for the first experiment, you calculate the resultant vector and show it does or does not match the value obtained from experiment.

You may need to construct neat tables top place your calculated quantities using a spreadsheet. Results of experiment must be presented graphically. Graphs are to be plotted in Excel and include gridlines. (When plotting a graph, chose a scale that is a multiple of 1, 2, 5, or 10). Computer usually does this automatically. The graph must have a title indicating the quantities represented, the X and Y axis properly labeled with the quantity and units, and the best straight line or curve drawn through the data points. (The curve or line must take up most of the space allotted for the graph). The graph must be large enough to extract data from it. (If you have a straight line, include equation and correlation coefficient (r-squared)).

Frequently, you will need to do something with data in order to put it into useful form. This may include answering questions, doing arithmetic or algebra, completing tables, or making graphs.

A sample calculation must be included in the lab report, even if you use a calculator or spreadsheet.

In addition, you must give all measured and calculated values some for of physical units. These values must be labeled appropriately.

Questions: Show all work or give full explanations for each question. Whenever a lab asks you to compare an experimental or observed valued with a theoretical or accepted value, you should use the following to determine the percent difference:

The electrostatic force that stationary charged objects exert on each other depends on the amount of charge on the objects and the distance between them (See Section 18.5 Coulomb’s Law, textbook Chapter 18 and Lesson 3).

Each point charge exerts a force on the other in Figure 18.10. Regardless of whether the forces are (a) attractive or (b) repulsive, they are directed along the line between the charges. In this experiment, you will utilize Coulomb’s force equation (See page 543 for the variable descriptions) to determine the net electrostatic force on one charge on the corner of an isosceles triangle when the other charges on the other two corners are fixed in space.

Only the one charge is allowed to move; its movement and direction after one second duration is governed by Coulomb’s law. Remember that the Coulomb force is a vector with units of N and is directed along the line of the two charges. Example 5 on pages 546-547 of your textbook will help you in solving this simulation problem.

You are to determine the net electrostatic force and direction on the red charged object after an elapsed time of 1.00 s caused by the electrostatic interaction of the fixed-in-space green and blue charged objects.

Lab Answer Sheet

Lab 1

Fc = ____________ .png”> = __________

Lab 2


Lab 3

(a) Trajectory:

(b) E || .png”>? _____ Yes _____ No. Proof: ________________________ _____________________________________________________.

E ||v? _____ Yes _____ No. Proof: ________________________ ______________________________________________________.

E ||p? _____ Yes _____ No. Proof: ________________________ ______________________________________________________.

E ||a? _____ Yes _____ No. Proof: ________________________ ______________________________________________________.

Physics_Lab_1_2_3.doc (40 KB)

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