Activity 8b - Electric Field Exploration

Transcription

1 Name Date Activity 8b - Electric Field Exploration Pd Go to the following website: Find the heading Run our Simulations and click On Line. Under the Simulations heading, select Electricity, Magnets, & Circuits. Click on Charges and Fields and when the web page loads click Run Now. A screen like the one shown below should appear. From the charge containers, you can select different quantities of negative and positive charges to place on the screen. You simply "grab" the charge with your mouse and drag it to where you want it on the screen. If the screen begins to get too crowded with markings you can select Clear All to remove all charges and other markings. You can improve your estimation of distances on the screen by adding a grid in which the minor lines represent increments of 10 cm and the major lines represent 50 cm. To do this, check the box labeled grid. Modeling Workshop Project STL Group 1 E1A8b_Electric Field Exploration_v1_DLP/RR10H

2 I - Exploring field around a point charge Place one positive charge (+1 nc) centered on an intersection of grid lines in the middle of your screen. 1. Select an E-Field sensors from the box, and drag the sensor around the charge. What do you notice about: a) the direction of the arrow at all times? b) the magnitude of the vector (the length of the arrow) as you move farther away from the charge? c) What does this arrow represent? 2. When you release the mouse button, the field vector will remain on the screen. a) Create four field vectors of identical length, with one to the left, one to the right, one directly above, and one directly below the charge. What do the four points have in common? b) Place a field sensor one major gridline (50 cm) to the right of the point charge. Now, place a second vector 100 cm to the left of the charge. Compare the length of the two vectors. What can you conclude about the relationship between electric field strength and distance? c) If you place a field sensor 150 cm to the left of the point charge, how will the electric field strength compare in size to the first vector? Test your prediction. 3. Keeping this picture in mind, remove the field sensors from the screen. Check Show E-field. a) b) c) What happens to the strength of the field as you get farther from the charge? Modeling Workshop Project STL Group 2 E1A8b_Electric Field Exploration_v1_DLP/RR10H

3 4. Uncheck Show E-field and replace the positive charge with a negative charge. To do so, drag the positive charge back to its container and drag one out of the negative charge container. Repeat steps 1, 2, and 3 for the negative charge. Enter your results below Step 1 Step 2 Step 3 5. Go to the following website: The window to left shows another representation of the electric field around charged object using what are referred to as electric field lines. Select the Show Electric field lines buttons. The green dot is a test charge used to probe the electric field. When you move it around the field, the attached arrow will serve the same purpose as the field sensors in the other applet. a. Examine the electric field due to a single positive charge. Modeling Workshop Project STL Group 3 E1A8b_Electric Field Exploration_v1_DLP/RR10H

4 b. Examine the electric field due to a single negative charge. c. Examine the electric field due to a two equal positive charges. Modeling Workshop Project STL Group 4 E1A8b_Electric Field Exploration_v1_DLP/RR10H

5 d. Examine the electric field due to a two equal negative charges. e. Examine the electric field due to a equal unlike charges. Modeling Workshop Project STL Group 5 E1A8b_Electric Field Exploration_v1_DLP/RR10H

6 6. II - Exploring field around parallel plates Return to the PhET simulation. While the software does not create charged metal plates, we can approximate a charged plate by lining up a number of charges. 1. Build two plates of opposite charge as shown below. Examine the electric field using the E-field sensors. Check Show E-field. Based on the information from the field sensors and the E-field shown, how would you represent the electric field with electric field lines? On the picture above, sketch the field lines for the electric field created by this configuration of charges. When you have completed your sketch, go to the website: For this simulation, you use a shift-click to add a positive charge and a control-click to add a negative charge. Use these tools to build a charge configuration like the one shown above. This simulation will show the electric field lines for your charge configuration. How does the electric field displayed compare to your configuration? Make any necessary modifications to your diagram. Conclusion: Based on your results from activity 8a and your online exploration of electric fields from activity 8b, compare the various representations of the electric field that are demonstrated in these activities. Write this on a separate page. Modeling Workshop Project STL Group 6 E1A8b_Electric Field Exploration_v1_DLP/RR10H