Day 9 - Electric Flux and Dipole moments

We simulated our own electric field with a square of nails, and the amount of nails we had to encompass within the wire determined our angle theta. We had angles ranging from 0 to 90 degrees, and the amount of nails came in multiples of 7.

Graph of # of Nails vs Angles between normal and electric field vectors; a manual fit of a sine/cosine curve works best-

Section 11.7 Activphysics - Electric Flux

Question 1: Flux Into or Out of an Oval
Design your own experiments to see how electric charge affects the flux into or out of the oval. In your experiments, you can:

• change the shape of the oval;

• move the center of the oval so that it surrounds the charge or does not surround the charge; and

• change the magnitude and sign of the electric charge.

When finished, develop in words a qualitative rule to determine the electric flux flowing into or out of the oval. Give examples to support your statements. When finished, compare your thinking with that of the Advisor.

There was a directly proportional relationship, since the flux followed the charge value of the inside of the ring consistently, whether it was zero, positive, or negative.

Question 2: Electric Flux with Two Charges
In the simulation, click the "two charges" configuration. You can now adjust the sign, magnitude and separation of two electric charges. Repeat the experiments such as done in Question 1 to see if your rule applies for this two charge system. You can:

• change the shape of the ring;

• change the position of the center of the ring (move it all over); and

• change the magnitudes and signs of the electric charges.

When finished, compare your thinking with that of the Advisor.

The dual charge examples seem very similar to the single charge examples. The flux follows the ring's inside charge whether it is positive or negative. If the charge was zero there was no flux.

Question 3: First way to determine electric flux
Change the simulation back to "one charge." The meter indicates the electric flux Φ into or out of the oval and the net electric charge Q inside the oval.

• What happens to the flux if you double or triple the positive electric charge inside the oval?

• What happens to the flux if you double or triple the negative electric charge inside the oval?

• Find an equation with a proportionality constant that relates the electric flux into or out of the oval and the electric charge inside the oval.

After answering the questions, compare your thinking with that of the Advisor.

When the charge is doubled or tripled the flux also increases accordingly. This is true for the positive and negative aspects. Thus we know that flux has a direct propotional relationship to the net charge in the ring.

Question 4: Second way to determine electric flux
The green electric field lines represent the electric field surrounding the source charges. Develop a rule for the electric flux passing out of or into the oval by counting the electric field lines passing out of or into the oval. After answering the questions, compare your thinking with that of the Advisor.

-The amount of field lines traveling out or inside of the oval/ring is proportional to the flux.

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