D2L-Exp3

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Broward College *

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2054

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Electrical Engineering

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Apr 3, 2024

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Charges and Fields – Potential Professor Dhiraj Maheswari February 5 th , 2024

Purpose The purpose of this lab is to understand the concept of electrical value potential and its relationship with distance and magnitude of charge. In this lab, students can visualize equipotential lines using the PhET simulator and determine electric potential due to multiple charges. Introduction As observed in the previous labs, opposite charges attract and like charges repel. It is also understood that the direction of field lines point radially inwards around negative charges and radially outward around positive charges. Lastly, these field lines are inversely related to distance therefore as distance from the point increases, force decreases. Procedure 1. Open the simulation using the link to PhET Interactive Simulations at the University of Colorado Boulder: PhET Interactive Simulations 2. We have used the same simulator in our investigation for Electric filed. Explore the options available in the simulator for Electric Potential. Data and Evaluation PART 1: Electric potential and Equipotential lines 1. Refresh simulation. Select +1nC charge. De-select Electric field. Click on Voltage, Values and Grid. Select Voltmeter.

2. Keep voltmeter at a distance of 2 meter away from charge. What is the value of potential at this point? Calculate potential using formula of electric potential. Do both values match? V=k(q/r) K= 8.99 x 10 9 Q= +1 nC R= 2 8.99 x 10 9 (1 x 10 -9 /2)=4.495 V The value from the simulation is 4.487V so they are extremely close! 3. As the voltmeter is moved away from charge, how does the value of the potential change? As the voltmeter is moved away from the charge, the value potential decreases. This is because the electric field around positive charges is oriented radially outward. At 4. Keep voltmeter at one point. Take +1nC more charge and keep it on earlier +1nC charge. How does the potential change? The initial potential with +1nC at 4 meters is 2.244V. When +1nC is added, the value potential becomes 4.487V, which means it doubles.

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5. Keep voltmeter at same point. Remove all positive charges. Now take -1nC charge. What is the value of potential? Do you observe any change? When the positive charges are removed and replaced with -1nC, the value potential is the exact opposite, -2.244V. 6. Click on pencil symbol of Voltmeter for equipotential line. What is the shape of this line? Click on several points on this line to check if the values of potential are same at all points. When the pencil is clicked, a green circle appears the charge like a radius. All along the line, the value potential measures -2.244V as long as the distance from the charge is the same. 7. Move the Voltmeter further (or closer) and click again on the pencil symbol. What did you notice? When the voltmeter is moved closer, the value potential becomes stronger. As we currently have a -1nC, the value becomes more negative as we move closer. Negative charges field lines radiate inwards. PART 2: Electric potential versus distance 1. Make a +3 nC charge and place it so that it is at the intersection of two of the heavier gridlines. This way, you can place sensors at fairly specific distances away from the charge. 2. Use the Voltmeter and the pencil symbol to measure and record in Table 1 the potential at the distances specified. Table 1 r (m) E (V/m) 1 26.96 2 13.52 3 9.002 4 6.744 5 5.401 6 4.498 7 3.858 8 3.386

8. Plot a graph Electric potential versus the distance using Vernier Graphical Analysis and insert it in your completed laboratory report. 9. How the potential depends on the distance? Include your findings and conclusion in the completed lab report. 10. For a positive charge, electrical potential is positive and decreases with distance. PART 3: Electric field of multiple charges

1. Create an electric dipole by placing one positive and one negative charge on a horizontal grid line. Measure the electric potential at the point midway between the charges and at several points on the vertical line bisecting the line segment connecting the charges. Directly between the charges, the equipotential is zero. As you move one meter to the right towards the positive charge, the equipotential reads 5.915V. As you move left towards the negative charge, it reads the exact opposite, -5.915V. 2. Create a charge configuration similar to that of a dipole but use two charges of the same sign instead. Measure the electric potential at the point midway between the charges and at several point on the vertical line bisecting the line segment connecting the charges.

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With two positive charges as opposed to opposite charges, the midpoint reads 8.960V. One meter to the right reads 11.91V and one meter to the left reads 11.91V as well. As you get closer to the charges, the equipotential increases. Results and Conclusion The simulation allows visualization of charges and fields. Last week, arrows and shades created a visual for strength as well as direction. This week, equipotential is measured using the simulation’s voltmeter. This voltmeter is useful to understand that between common charges, the midpoint is also the median equipotential. If the voltmeter moves closer to one side, the value of potential increases. This differs when the charges differ. If one charge is negative and one charge is negative, the midpoint is 0.00 V. Varying from the midpoint towards the positive charge, the value increases but if moved towards the negative it decreases at the exact same rate.

Using another graphic, the pencil, the simulation offers another visual aid to show how the value potential exists in around a charge like a radius. If the distance from the charge is the same, the value potential will also be the same.