Lab 1

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University of Texas, Rio Grande Valley *

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Electrical Engineering

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Feb 20, 2024

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Lab 1 – Static and Current Electricity Virtual Lab Name : Group 5: Esteffy Velasco, Evelyn Yanez, Marissa Zuniga, Marc Garcia, Joshua Villarreal Basic Concepts Static electricity , a natural phenomenon, has been known since at least as early as the 6 th century B.C., as discussed by Thales of Miletus, a pre-Socratic Greek philosopher and one of the Seven Sages of Greece. The name electron comes from the Greek word amber, a fossilized tree resin. When rubbed with fur, a piece of amber can attract small objects like tiny pieces of paper. When rubbed many materials exhibit this same behavior, ability to attract small objects. Today we know that the source of this attraction is due to the presence of static electric charge. Electric charge comes in two forms: positive and negative. Electrons carry negative charge and protons carry positive charge. Normally materials are electrically neutral; that is, they have an equal number of positive and negative charges (equal number of protons and electrons). From a microscopic point-of-view, a material is comprised of atoms. An atom is composed of electron(s), proton(s) and neutron(s). Electrons are relatively light, mobile and easily removed from the core nucleus that is comprised of relatively massive proton(s) and neutron(s) that are strongly bound together. Static electricity occurs whenever there is an accumulation of one type of charge and may be produced two dissimilar insulating materials are rubbed together: for example, plastic and fur. A static charge is produced when electrons are transferred or removed from one object and placed on the other. The material losing electrons has fewer electrons than normal and becomes positively charged. The material gaining electrons now has more electrons and becomes negative. Surrounding a charge is an electric field that becomes weaker as the distance from the charge increases. For positive charge, the field lines are directed outward from the charge. For negative charge, the field lines are directed inward towards the charge. When a second charge is placed in proximity to a first charge, a force is imposed on the second charge through the electric field of the first charge and a force is imposed on the first charge through the electric field of the second charge with these two forces being equal in magnitude but opposite direction. For similar charges, both of them being positive or negative, the charges repel one another. For opposing charges, one negative and the other positive, the charges will be attracted to one another. If a neutral material is placed inside a weak, negligible, electric field, it will not experience a net force because the material contains an equal number of positive and negative charges. However, if a neutral material is placed inside a strong electric field the material may become polarized and experience a net force. A material may become polarized because the dissimilar charges will be attracted toward the charge(s) while similar charges will be repelled away from the charge(s) producing the electric field; thereby, the material becomes polarized whereby the charges in the material are no longer randomly distributed and are slightly separated (positive on one side, negative on the other side). Since the strong electric field surrounding a charged object becomes weaker with distance from the charge object, the object experiences a net attractive force due to the from the closest charges of opposite sign as compared with the weaker repulsive forces on like charges that are further away. As an example of such polarization effects, a balloon may become charged by rubbing it in your hair. If the balloon is then placed against a neutral wall, it may then stick to the wall and defy the forces of gravity.

Activity 1 : Static Charge: You will use the Charges and Fields PhET lab to map the electric field around one or more-point charges at rest. Link: https://phet.colorado.edu/en/simulation/charges-and-fields Learning Goals : Students will be able to ● Determine the variables that affect how charged bodies interact ● Predict how charged bodies will interact ● Describe the strength and direction of the electric field around a charged body. ● Use free-body diagrams and vector addition to help explain the interactions. Beginning Observations 1) Open the Charges and Fields PhET simulation. Drag a positive charge to the center of the screen. Then drag the ‘Sensors’ (yellow dot) somewhere in the screen. 2) What do the “E-field sensors (yellow dot next to charges)” show? It follows the direction of the positive charge. 3) Select on ‘Values’. What does it show? How does this number change if you move the Sensor closer to the charge? It shows the degree and the v/m. The electric field is made up of 4 quadrants. Depending on where you put the E-field sensor, changes the number of degrees and v/m. If you move the e-field sensor away, in the top right quadrant, from the positive charge the degree increases while the v/m decreases. 4) For this lab, q=1nC. How can you create a charge of +2q? -3q? in the screen. Part 1 – Field around isolated point charges Click on the reset button (bottom right). 5) Take a screenshot of field lines for the scenarios below. Make sure you are sketching continuous field lines. 4q -2q

Part 2 – Field around two point charges in a line 6) Take a screenshot of field lines for the scenarios below. Make sure you are sketching continuous field lines. Two unequal, unlike point charges separated by some distance Two equal point charges separated by some distance 7) When you have two like charges in a line (separated) – where is the electric field the greatest? Is there ever a point where the field will be zero? The electric field is the greatest where the closest the charges are to each other. There will be a zero charge in between the two charges. 8) When you have two unlike charges in a line (separated) – where is the electric field the greatest? Is there ever a point where the field will be zero? The electric field is the greatest where the closest the chargers are to each other. The field will never be a zero charge when there are to unlike charge together Part 3 – More complicated scenarios 9) For this part of the lab, create following arrangements of your choice and submit screenshot of the field lines. (1) 3-point charges, equal, like charges in the shape of an equilateral triangle. (2) 4-point charges, 2 positive, 2 negatives, all unequal at four corners of a square.

Place two sensors at places of your choice and explain in the second row why do you think the sensor is pointing the way it is. Place two sensors at places of your choice and explain in the second row why do you think the sensor is pointing the way it is. Since all charges are alike the charge in between them all is at a zero. The 1st sensor is following the direction of the left corner charge. The 2nd sensor is in the middle of all three but still following the top charge. Although it may seem the 1st sensor being closer to the negative charge it is still being hit by the positive charge. And with positive charges the electric field pushes away from its charger same goes for the 2nd sensor. Conclusion Static Electricity : As you answer the questions on Static Charge, explain in your own words why your answer makes sense and provide evidence from your Static Charge experiment. Add more experiments to Static Charge if you need to get better evidence. Activity 2: Ohm’s Law Lab Objectives : After completing these lab activities, students will be able to: 1. State Ohm's law 2. Solve for each variable in Ohm's law 3. Describe what happens to the current of a circuit when either the voltage or resistance is increased or decreased Brief Concepts : Ohm’s law : Current flowing through a resistor is directly proportional to the potential applied across it. 𝑉 = 𝐼𝑅, 𝑤ℎ??? 𝐼 𝑖? ??????? 𝑎?? 𝑅 𝑖? 𝑅??𝑖?𝑎??? 𝑎?? 𝑉 𝑖? ?ℎ? ??𝑎???? ?? 𝑉???𝑎?? 𝑎???𝑖?? 𝑎????? 𝑖? Series connection : Cells are joined end to end in a series connection. Positive terminal of a cell is connected to negative terminal of the next cell. In this virtual lab, you will be using these two links to complete your lab activity . https://phet.colorado.edu/sims/html/ohms-law/latest/ohms-law_en.html

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