Lab 3

TA: Keslo Estil SEC#: Name:

Lab 3. Electric Field and Potential

Coulomb's Law describes the force that one charged particle exerts on a second charged particle. A more useful description includes the role of the electric field. It is preferable to say that the first particle produces an electric field in the space around it, and if a second particle is placed in this space, the field exerts a force on it. The strength of the field, E, at the location where the second particle was placed is defined as the force on that particle divided by its charge. A second related field that characterizes the space is electric potential, V. The relation between the two is that E is the "gradient" of V (the rate of change of V with position).

In this experiment, you will be mapping the potential in the space around a pair of charged objects and determining what information can be extracted regarding the associated electric field.

· Experiment link: https://phet.colorado.edu/sims/html/charges-and-fields/latest/charges-and-fields_en.html

Preliminary Questions (1 - 4)

Procedure:

1. Place a pair of charges, positive and negative on the simulation grid paper, and note how the potential changes as you move the probe from point to point with the Equipotential meter. Record how far the charges are from each other with the Tape Measurer.

2. Map the +2V equipotential line by locating where the meter reads 2 V. Make a note of the coordinates on the grid paper where this occurs. Repeat for the 3, 4, 5, 6, and 7 V equipotential lines.

3. Repeat the above procedures (#1,2) for two pairs of charges.

4. Repeat the above procedures (#1,2) for two of pairs charges again, but positive with negative, and negative with positive.

Analysis:

1. Describe the electric field between the first equipotential map. Are there regions where it appears uniform? non-uniform? What is the value of E midway between the centers of the charges?

2. From the "density" of the electric field lines seen in the second two maps, how can you tell where E is large and where it is small?

3. From the spacing between the equipotential lines seen in the second two maps, how can you tell where E is large and where it is small?

Note: Include very clear screenshots for the graphs to receive full credit.