LAB 8. ELECTRIC FIELD AND POTENTIAL

A. Determine the relationship between electric potential and distance for a point charge.

B. Determine the relationship between electric field and distance for a point charge.

B. Determine the relationship between the electric potential and the electric field strength in a region.

DIRECTIONS:

Open Charges and Field simulation. (Video tutorial attached at bottom)

Click to play. Once the simulation opens, check the box: VALUES and GRID

PART I.

TASK: To develop the relationships between V and r and between E and r.

1. First, explore by placing a 1 nC positive point charge in the middle of the screen.

2. Move the voltage probe box to different locations near the charge.

3. Replace the positive point charge with a negative point charge. To remove charges, drag them back into their box.

Question 1: How does the voltage number change?

Question 2: How does what the voltage probe box show differ with the negative charge? How is it the same?

DATA

1. Use the tape measure to measure the distances from a field-creating charge to a test charge

(the test charge is next to the charges and is called ‘sensor’).

2. The tape measure can be dragged to a specific distance and placed anywhere on the field.

3. Take at least 10 data points (distance, E, V) and record them in a data table. Include units on your measurements.

GRAPHS

• Plot a graph of V vs. r
• Determine the relationship between the electric potential and the distance from the source charge that produces it.
• Plot a graph of E vs. r
• Determine the relationship between the electric field and the distance from the source charge that produces it.

Question 3: Based on your data in the simulation, where is the electric potential equal to zero for a single point charge?

Does this change based on whether the source charge is positive or negative?

PART II.

TASK: To develop a procedure to test the relationship between electric potential and E field strength.

Question to answer: when you make equipotential curves, how does the spacing relate to E field?

1. First, explore by placing a 1 nC positive point charge in the middle of the screen.

2. Move the voltage probe box to different locations near the charge and click on the PENCIL to plot the equipotential.

3. Note that the electric potential is the same everywhere on each curve but different on different curves depending on how far the curve is from the 1 nC point charge. You can confirm this by moving the cross hairs of the voltage probe box around the curve and reading off the voltage value.

4. Next, use charges, the voltage probe box, tape measure, and E field sensors to determine the relationship between the strength of the electric field in a region and the spacing of equipotential curves.

For example, for a given ∆V between curves, are the equipotential curves farther apart in a region of a strong E field compared

to a weak one? What happens when they are closer together?

Is an equipotential configuration independent of E field strength?

PROCEDURE: Write the procedure with enough detail so someone familiar with the simulation could duplicate your experiment with no additional directions.

DATA: Record your data. Include at least 6 data points (distance, E).

CONCLUSION: Show calculations to support your conclusions about the relationship between the spacing of the equipotential lines and the electric field magnitude at that location in space.