Virtual Activity: Equipotential Surfaces

Goal: Gain an increased understanding of the electric field caused by various charge configurations.

Type of Activity: Structured Inquiry 

Materials Needed: Electric Field Simulation

Activity:
Like you did in the virtual activity on Electric Fields, you will drag charges out of the charge bin and place them in the virtual space. After your charges are in place, you can drag the electric potential measuring device (the blue box with the target locator on top) to any location in the field and press the "pencil" button on the device to plot a 2 dimensional equipotential line. Once you know how to use the simulation, perform the following trials.

Trial 1:
Place one positive charge in the virtual space. The charge magnitude is 1 nC (1 x 10^-9 C). Choose a location in the vicinity of the charge and, with the electric potential measuring device, plot an equipotential line (click the pencil). Record the electric potential in the data table. Move the electric potential box to a second and third location and plot more lines, each time recording the new potential. Use the measuring tape tool to find the distance from the charge to each equipotential in centimeters. Convert the measurements into meters. Record these measurements in the data table. Take a screenshot of the simulation showing the central charge and the three equipotentials. Include this screenshot in the lab report. Use the electric potential equation discussed in the previous presentation to calculate the potential of each equipotential line. Show these calculations in the data analysis section of the lab report and then answer these questions in the conclusion section:
A. What is the shape of each of these 2-D equipotentials?
B. What equipotential shape would form if you were using 3-D space? 

Trial 2: Clear the virtual space and then add one negative charge to the simulation. Create three equipotentials. Take a screenshot of the simulation showing the central charge and the three equipotentials. In the conclusion section of your lab report state how the equipotentials in trial 1 compare to those in trial 2. 

Trial 3. Clear the space again, then place one positive charge and one negative charge in the simulation. Use the electric potential measuring device to construct an equipotential field map of many lines. Make sure you find the equipotential line that is equidistant from each charge. Place two E-Field sensors (the yellow dots in the charge bin) on each equipotential line. Take a screenshot of the simulation showing the charges, the equipotentials and the sensors. Respond to these questions in the conclusion section of the lab report:
A. What do you notice about the orientation of the E-field in relation to each equipotential line?
B. Does the E-field magnitude depend on its position for a particular equipotential? Explain your answer.
C. Does the magnitude of the electric potential increase or decrease when you "follow the field" from one equipotential to another? Explain your answer conceptually.

Trial 4. Clear the space again. Place two negative charges in the simulation. Use the electric potential measuring device to construct two separate equipotential lines whose electric potentials are -14.900 volts. Use it again to produce another equipotential line whose electric potential is -9.325 volts. Finally, use it to construct an equipotential line whose electric potential is -12.450 volts. Place two E-Field sensors on the -12.450 volt equipotential line. Click the "values" button in the control panel to show the electric potentials. Take a screenshot of the simulation showing the charges, the equipotentials, and the sensors. Respond to these questions in the conclusion section of the lab report:
A. Why does the simulation show two equipotential surfaces of -14.900 volts and only one equipotential surface of -9.325 volts?
B. Does the electric field magnitude on the the -12.450 volt equipotential line have different magnitudes at different positions? Explain why or why not.

Trial 5. Clear the space and then add a complicated arrangement of 3 positive and 3 negative charges. Add numerous equipotential lines. Take a screenshot showing the charges and the equipotentials. State a data-supported observation about the electric field of your arrangement in the conclusion section of the lab report.