Physics

Electricity and Magnetism Simulation Worksheets and Labs

Physics 152 Online, CSU Long Beach

Dr. Thomas Gredig

Copyright c© 2016 Thomas Gredig ALL RIGHTS RESERVED. PUBLISHED BY THOMAS GREDIG

THOMASGREDIG.COM

ALL RIGHTS RESERVED. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without explicit written permission from the publisher. Edition, June 2016

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.1 Activity Worksheets 8

1.2 Hands-on Experiments 8

1.3 Team Work 10

2 Lab Report Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.1 Online Lab Organization 13

2.2 Report Structure 13

2.3 Report Submission 15

2.4 Grading Rubric 15

2.5 Measuring Data 15

2.6 Ethics 16

2.7 Experiments 16

2.8 Arduino 16

2.9 Fitting Data 17

3 Practice Exams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.1 Problem with Solution 21

3.2 Midterm Practice Problems 22

3.3 Final Exam Practice Problems 23

3.4 Basic Relations in Electricity and Magnetism 24

3.5 Reference 26

I Interactive Simulations

4 Activity 14: Electric Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4.1 Objective 33

4.2 Background 33

4.3 Prediction: Charge Configurations 34

4.4 Calculation 35

4.5 PHeT Simulation 35

5 Activity 15: Electric Field Hockey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 5.1 Prediction 37

5.2 PhET simulation 39

5.3 Evaluation 39

6 Activity 16: Electric Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 6.1 Prediction 41

6.2 Simulation 42

6.3 Evaluation 42

7 Activity 17: Electric Field from Irregular Shape . . . . . . . . . . . . . . . . . . 43 7.1 Background 43

7.2 Prediction 43

7.3 Calculation 44

7.4 Evaluation 44

8 Activity 18: Light Bulbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 8.1 Prediction 47

8.2 Mesaurements 49

8.3 Evaluation 50

9 Activity 19: RC Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 9.1 Background 53

9.2 Predictions 53

9.3 Measurements 54

9.4 PhET Simulation 56

10 Activity 20: Series and Parallel Resistors . . . . . . . . . . . . . . . . . . . . . . . . 59 10.1 Series Circuit in a Parallel Circuit 59

10.2 Parallel Circuit in a Series Circuit 60

10.3 Series Circuit in a Parallel Circuit in a Series Circuit 60

11 Activity 22: Faraday’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 11.1 Background 63 11.2 Bar Magnet 63 11.3 Electromagnet 65 11.4 Pickup Coil 65 11.5 Transformer 66 11.6 Generator 67

12 Activity 23: Radio Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 12.1 Prediction 69 12.2 Simulation 69

II Hands-on Experiments

13 Lab 1: Measuring Charges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 13.1 Tools 75 13.2 Prediction 75 13.3 Experiment 76 13.4 Evaluation 76

14 Lab 2: Magnetic Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 14.1 Tools 77 14.2 Prediction 77 14.3 Experiment 78 14.4 Evaluation 78

15 Lab 3: Arduino Battery Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 15.1 Tools 79 15.2 Prediction 79 15.3 Experiment 80 15.4 Evaluation 81

16 Lab 4: Resistor Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 16.1 Tools 83 16.2 Prediction 83 16.3 Experiment 84 16.4 Evaluation 84

17 Lab 5: Voltage Divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 17.1 Tools 85 17.2 Prediction 85 17.3 Experiment 85

17.4 Evaluation 86

18 Lab 6: RC circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 18.1 Tools 87 18.2 Prediction 87 18.3 Experiment 88 18.4 Evaluation 88

III Team Tasks

19 Team Task 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 19.1 Relevant Chapter 93 19.2 Electron mass 93

20 Team Task 15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 20.1 Midterm Preparation 95

21 Team Task 17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 21.1 Electric Field of Any Shape 97

22 Team Task 19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 22.1 Resistor Network 101

23 Team Task 21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 23.1 Problem Solving 103

24 Team Task 23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 24.1 Reflections 105

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

1. Introduction

UNDOUBTEDLY experiments provide an real value to any learning experience as a way ofconnecting the real-world with the abstract. This is particularly true for the topic of “Electricity and Magnetism”, which deals with quantities that are very real, electric and magnetic fields, but our senses are poor at measuring (although for electromagnetic waves in the visible range, our eyes help).

Experiments, however, can be complex to setup and costly. An intermediate experience, therefore, are interactive simulations. These are computer programs that have programmed algorithms, which simulate certain settings. Many simulations are available nowadays, but I would like to point out a particular project, which was sponsored by the National Science Foundation, and developed by the University of Colorado, it is called the PhET simulations, available at https: //phet.colorado.edu/. A collection of interactive simulations for the Sciences and Mathematics made available to the public through federal science grants. We provide you with a set of worksheets that guide you using these simulations in part I starting on page 33.

In addition to the simulations, the online PHYS 152 lab includes hands-on experiments detailed in part II starting on page 75. The procedure for these labs is detailed in Chapter 2 starting on page 13. It is based on a home experimental kit and so all experiments can be performed with the help of this kit, a smartphone, computer, and everyday tools. Indeed, the aim of this series of small experiments related to discovering electricity and magnetism is to make the procedures applicable, so that you can carry out many more of the same type of experiments on your own. Therefore, this course provides only the beginning boundaries of much more exploration. A home kit is therefore ideal as it gives you some tools needed to continue this scientific process.

Lastly, science and engineering are highly collaborative disciplines with team tasks. Sharing, communicating, and evaluating each other is an everyday task of professionals in this field. A paradigm for this is research. It is based on proposals of experiments that are evaluated and vetted based on their merits and benefits. The best experiments are conducted, data is acquired and a lab report is submitted for publication. Peers review these reports before some are accepted for publication. You have the opportunity to practice and learn this process in small teams using an asynchronous discussion forum. The teams are small (around 5 participants) formed by the

https://phet.colorado.edu/
https://phet.colorado.edu/
8 Chapter 1. Introduction

instructor. The team will work on team tasks (see part III on page 93) using team roles that are mapped to the specific steps of problem solving.[4, 3] These roles are explained on page 10, with the underlying understanding that an expert wears all hats at the same time, but for a learner focusing on one role will be good practice. Additionally, we will use these teams to evaluate lab reports. The team will give feed-back based on the lab report grading rubric (page 15) to selected lab reports. This mechanism provides multiple benefits, for one you get to see how your peers write reports, normalizing your experience, applying the grading rubric focuses your attention to critical portions of the report, and finally you can received feed-back from teams to improve your reports. Lastly, this process mirrors the professional approach and eases a pathway into a career.

1.1 Activity Worksheets The following worksheets will provide you some guidance as how to use those simulations and others by asking questions. For the purpose of effective learning, it is important to first reflect on your current knowledge. This is generally done by making predictions, which is to think about different scenarios related to the topic and based on your knowledge foresee outcomes. You may be tempted to guess the answer without much reflection, or look up the solution.[5] Resist this temptation, as this step is crucial in memory building. It is important to write those predictions down. In the next step, you will use the simulations and recreate the questions, then make observations of the results. In the third step, you will compare the predictions with the observations and note any discrepancies. In the last step, you reflect on your findings and try to apply the learned experiences to other settings, which are similar. If done properly, this procedure is extremely efficient. Essentially, you know that learning would occur, if your predictions would be different in some way from your observations. Note that sometimes, seemingly the predictions agree with your observations, there are fine discrepancies, or nuances, that are different, scientists and engineers are good at detecting those details and ponder about them. During the course, different activities are assigned with specific deadlines. Submit your worksheets as single PDF files that you can easily scan with one of many available PDF scanners. From your phone, you can use CamScanners, GeniusScan, etc. there are other ways as well. You can either print the worksheets and directly work on them, using the space, or you can use separate sheets for your answers. Always make sure (to get full points) that you label all the questions in accordance to the numbering scheme from this worksheet. For every activity, you may also be asked to capture a screenshot of the simulation and include it. For full points, capture and submit a unique screenshot that shows that it is your work. It is also important to label the axes of all graphs and include units as well. Some examples are given in the worksheets.

1.2 Hands-on Experiments There are several experimental hands-on labs that can be carried out at home. The first step will be to clarify the experimental procedures and writing down the predictions. In your notebook, you write down the procedure of how you will carry out the experiment, the hypothesis, and the predictions. In the next step, you build the experiment and take data. Commonly, data needs to be taken several times in order to verify the experimental procedure and the reproducibility. The repetition also gives you a way to judge the reliability of the data and the error bars. During the experiment, all results are carefully noted in the lab notebook. At this point, you are ready to write the report according to the guidelines listed on page 13; scientists and engineers use this method and you can find many sample reports at https://arxiv.org/. We strive to learn from the experts. Note that the report provides both details about the experimental method used, the results, and analysis. It also includes photos of the experimental setup with the date in the photograph, see Fig. 2.2.1. A lab report has graphs, which you can generate with OpenCalc (https://www.openoffice.org/

https://arxiv.org/
https://www.openoffice.org/product/calc.html
https://www.openoffice.org/product/calc.html
1.2 Hands-on Experiments 9

product/calc.html), Google Sheets (https://www.google.com/sheets/about/), RStudio (https://www.rstudio.com/), R-Fiddle (http://www.r-fiddle.org/#/), gnuplot (http:// www.gnuplot.info/), or Plot2 for Mac (http://apps.micw.eu/apps/plot2/). All of these programs are free, and several open-source, most can be installed on different platforms. The lab report is, then, an independent, complete summary of the experiment you conducted.

Before reports are published, scientists and engineers, peer-review the reports and give feed-back. In the course, this process is called “lab evaluations”, and you are responsible to review lab reports of your peers based on a rubric (see page 15). Reading your peer’s lab reports and evaluating them is a powerful learning tool that you should not underestimate. Not all reports will get published, based on the reviews and his or her judgement of the report, the editor (here, the instructor) will make the final evaluation of the report.

In order to make the experimental kit, or tool box, cost effective, we have adopted the micro- controller platform called Arduino. The Arduino controller is open-source and inexpensive (order of USD 10 – 20), widely available. There are many types of Arduino, for the course, the basic UNO type will be sufficient. The Arduino board comes with sensor inputs and also with outputs. We will use these sensors to connect resistor circuits, and test RC circuits. The board connects via USB port to a computer; details are provided on the website https://www.arduino.cc/ and the software is installed from the “Download” button.

1.2.1 Experimental Kit

You will need to purchase an experimental Arduino kit in order to perform the experiments. You have several options to purchase or build the kit. Reviewing the labs, you can see all the required tools and materials listed in part II starting on page II. Here is a summary:

• Arduino micro-controller with USB (http://tinyurl.com/phys152Arduino) • breadboard and wires • several resistors (1 kΩ, 10 kΩ, 1 MΩ) • one or more capacitors (0.5 µF or more, product of largest resistor multiplied with capacitance

should equal about 1 s) • basic compass (possibly compass of phone) • Al foil, drinking straws, other home materials

You can build your own kit based on the previous list, or you can purchase a package, which contains all of these items and a few more.

• Sunfounder Project Super Starter Kit for Arduino UNO R3 at tinyurl.com/phys152kit2 plus an Arduino Board at http://tinyurl.com/phys152Arduino

• Arduino UNO R3 Ultimate Starter Kit at tinyurl.com/phys152kit1 • KT003 Arduino UNO Start Kit with Bread Plate at http://tinyurl.com/phys152kit4

(does not include capacitor, see page 87)

Note that the Sunfounder Kit (tinyurl.com/phys152kit2) is probably the best and it includes 100 nF capacitors and one 5 MΩ resistor, which would give you a time constant of 0.5 s, a bit less than 1 s. However, if you put all 4 capacitors in parallel, you can quadruple the time constant by increasing the capacitance to 400 nF, which is quite sufficient.

You can also purchase capacitors and resistors separately from several stores and online from Mouser at http://www.mouser.com/, searching for multilayer “capacitors 10 uF”, you will find that the cost is less than one US dollar.

https://www.openoffice.org/product/calc.html
https://www.openoffice.org/product/calc.html
https://www.google.com/sheets/about/
https://www.rstudio.com/
http://www.r-fiddle.org/#/
http://www.gnuplot.info/
http://www.gnuplot.info/
http://apps.micw.eu/apps/plot2/
https://www.arduino.cc/
http://tinyurl.com/phys152Arduino
tinyurl.com/phys152kit2
http://tinyurl.com/phys152Arduino
tinyurl.com/phys152kit1
http://tinyurl.com/phys152kit4
tinyurl.com/phys152kit2
http://www.mouser.com/
10 Chapter 1. Introduction

1.3 Team Work In addition to individual assignments, there are some problems for small teams. For the teams to work cooperatively, we have implemented some features that will help with the asynchronous online discussions. In particular, we have assigned roles, which help you train each step of the problem solving (see section 3 on page 21). Note that an expert problem solver will rotate independently through all roles (team leader, planner, researcher, executive, and skeptic). In order to become or improve as an expert problem solver, it is important to practice / train each specific step independently. The grading and point distribution of the midterm and final exam is based on the problem solving steps or the roles outlined here. Once you master each step, you can put them together and gradually become an expert yourself. If you are interested in more details and the physics education research, you can read more in this booklet: http://groups.physics.umn.edu/physed/Research/CGPS/GreenBook.html Use the team work assignments to your advantage, namely to make learning more productive.[1] Somewhat surprisingly, the benefits, although different in aspects, are to all learners regardless of their prior expertise.

1.3.1 Team Roles Here is a summary of the team roles. You will be assigned different roles in different tasks. As a member of your group you work holistically, but focus on your specific role. • Team Leader: motivates team, sends messages to the team, makes sure the team understands

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