Physics 1bl Electric Potentials And Fields (Page 5 of 6) in pdf

Physics 1BL

Electric Potentials & Fields

Summer Session II 2010

b) Using your probe, find a point at the selected voltage on the Teledeltos paper.

c) Mark the location and voltage of that point on the white photocopied page. Use the

grid marks on the black paper to help transfer your readings onto the photocopy.

d) Repeat steps (b) and (c) until there are a sufficient number of points at that voltage to

“connect-the-dots” and form an equipotential curve. Be sure to investigate all over

the surface of the paper to find points with equal voltages.

e) Repeat for the other voltages selected to show a better picture of the equipotential

contours.

B2. Examine the shapes of the equipotential curves. First find the whiteboard from the

group that worked on the same shape charged conductors you used in activity B.

Do the shapes of the equipotential surfaces agree with those that were drawn in the

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whiteboard activity?

From these equipotential shapes, what do you predict the electric field lines will

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look like? Do these predictions agree with the electric field lines drawn in the

whiteboard activity? Why do you think that is?

Activity C: Finding the electric field from the direction of the

maximum change in electric potential

C1. For this activity, instead of the multimeter probes use black and red wires with banana

plugs at each end. Plug one end of the wires into the multimeter. Tape the other ends

together so they have a fixed separation and measure their separation. Now, touch the

two taped together banana plugs to the black paper. The multimeter reads the

potential difference (or voltage) between the two contacts - from the red plug to the

black plug.

• What would you expect the multimeter to read if you placed the plugs so that both

tips were touching the same equipotential surface?

• Place the plug so that both tips are touching one of the equipotential surfaces you

found. What potential difference does the electrometer measure? Does this agree

with your prediction?

C2. Rotate the plugs about that spot, keeping contact with the paper, until the voltage

reading on the multimeter is a maximum. Record the direction of maximum potential

difference with an arrow and the magnitude of the voltage on your white paper. Be

sure the direction is correct (from the red plug to the black plug).

• What is the orientation of your arrow with respect to the equipotential

surface?

C3. Find the magnitude and direction of maximum potential difference for several spots in

various regions on your paper (not just on equipotential surfaces), marking the

magnitude and direction on your white photocopied page.

Physics 1bl Electric Potentials And Fields Page 5