Physics Electric Field Simulation Activity Go to phet.colorado.edu and follow the “play with sims” link, then the “physics” link to the “charges and fields” simulation. Click “run now” to use the applet. 1. Place a 1 nC (nanoCoulomb) + charge and an electric field sensor in the arena. Click “ show E-­‐field to see field lines. Observe the arrow as you drag it around. 2. Put away the + charge and bring out a – charge. Observe the arrow and consider how it is similar to and different from when you used a + charge. 3. Drag the voltage probe box (at lower left) to different areas of your electric field (using both + and – charges with a single sensor, one charge at a time) and note how the voltage differs as you move it around. Click on “plot” to create lines of equipotential. 4. Place two charges in the arena and observe what happens to the strength and direction of the field. 5. Make two opposing parallel single walls of charges, one all + and the other all – and observe the electric field. 6. Try some different configurations, and, before you try them, brainstorm with other students to figure out what you expect to happen and why. 7. For a challenge, try the “electric field hockey” applet. Questions 1. What did the arrow emanating from the test charge in the presence of the + and – charges tell you. Refer to its length and direction. 2. How does voltage vary with the distance between the charge and the sensor? 3. What do the lines of equipotential tell you, what does this remind you of, and why do you think these things are similar? Explain why it is impossible for these lines to cross each other. 4. Use the tape measure to measure the distance between the charge and the sensor. It is a little fiddly, but play around with it and get it as close as you can. Create a data table with columns for distance (measured with the tape measure) and field strength (v/m) for 5 different distances. Create a graph for this in Excel, graph the line of best fit, and explain what it means. If you don’t know how to create a line of best fit in Excel, the following link has a good explanation (http://chemed.chem.purdue.edu/genchem/lab/datareports/excel/bestfit.h
tml). You may also check the Excel help files or just do a web search. 5. Add another charge to the field and repeat 4. What does this tell you? 6. Explain the behavior of the field strength arrow emanating from the test charge when you put 2 (or more) charges in the arena. 7. Place several charges in the arena and explain what happens to the electrical field. Draw a sketch of what you did to accompany your explanation.