Lab - Ohm's Law

Ohm’s Law INSTRUCTIONS: (1) Download this lab document and type out answers on the space provided for then save your answers. (2) If the spacing automatically moves, adjust so that your answers are not all over the place. (3) Upload this document, with your answers on it, on the designated Lab 9 Dropbox on Canvas Lab Reports/Module Tab. (4) If possible, ALL answers must in green font or highlighted in green. Do NOT delete anything in this lab document. Grading Policy for Lab Reports WITH Pre-/Post-lab Questions Completeness and accuracy of answers (with required screenshots) for the: 1. Warm-up and lab activities – 70% 2. Pre-/Post-lab questions – 10% 3. Conclusions and real-life applications – 20% Grading Policy for Lab Reports WITHOUT Pre-/Post-lab Questions Completeness and accuracy of answers (with required screenshots) for the: 1. Warm-up and lab activities – 80% 2. Conclusions & real-life applications – 20% This lab uses the Ohm’s Law simulation from PhET Interactive Simulations at University of Colorado Boulder, under the CC-BY 4.0 license Purposes/Objectives: In this lab, you will be able to: 1) explore the relationship between voltage, current, and resistance in simple electric circuit 2) relate the slope of voltage versus current (V vs. I) to the resistance of a wire. 3) verify Ohm’s law. Procedure: A. Electric circuit basic concepts: Ohm’s law: Current, I flowing through a resistor (with resistance, R) is directly proportional to the potential (voltage, V) applied across it. Mathematically, � = �× � or I=V/R or R=V/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. 2) Once Ohm’s law PhET Sim opens, your screen should look like the one below. Ohm’s Law 3) Explore using the sliders for voltage and resistance. The control panels are located on the right side of the lab area. The circular orange button at the bottom right corner is the Reset button. What did you discover? Write your answers below. Also, paste below screenshots to support your answers. By interacting with the simulation of Ohm’s Law, I discovered that if I increased the voltage, the current will also increase, as shown in the screenshot: In the same hand, if I reduce the resistance while keeping the same value of voltage, the current will continue to increase: Ohm’s Law Also, I could see that if I increase the resistance the current will decrease: And lastly, if I reduce the voltage while keeping that same amount of resistance, the current will continue to decrease: 4) Select a value of resistance (say 416 ohms, ). Now, increase the potential (say, 4.5 V) across resistor. How does current change? The mA unit for current means milliampere. Milli means 1/1000. Write your answer below. Ohm’s Law This is the set-up of voltage and current when we open the simulator: And here is now with the lower resistance while keeping the same voltage value: As we can see, when we lower the resistance, the current increases, showing an inversely proportional relationship between resistance and current. The current I is now of: I= V / R = I= 4.5 V / 415 ohms = I= 0.01084 Ampere I= 10.8 mA 5) Hit the Reset button. Select a value of potential (voltage). Now, increase resistance. How does the current change? Write your answer below. By increasing the values of voltage and resistance from their original (set-up) values, we could see two things. 1) If we increase first the voltage, we can see that the current increases; and 2) when we increase the resistance even more than the voltage, we see how the current is decreasing in value, just as shown in the screenshot: Ohm’s Law The current went from 10.8 mA to 7.0 mA by increasing the voltage but increasing even more the resistance. 6) If a battery of 9.0 volt is connected across resistor of 1000 ohms, what will be the value of current flowing through the circuit? Write your answer below. The current of the circuit will be of the 9.0 mA. I= V/R I= 9.0 V / 1000 ohms I= 0.0090 Amps I= 9.0 mA Ohm’s Law 7) For a resistor (resistance) of 172 ohms or so, apply five different potentials and measure the current through the resistor. Read the current this way: If you have a current of 8.7 mA, this needs to be recorded in the Data Table as 0.0087. Divide the current reading by a thousand. Clarification: I used a resistor (resistance) of 171 ohms, and modified some values of voltage 1.5 3.0 5.0 6.5 8.5 Potential or Voltage (Volt) 0.0088 0.0175 0.0292 0.0380 0.0497 Current (Amp) Plot Potential (�)y vs. Current (�) x curve on graph paper or Excel Spreadsheet. Paste the graph below inside the (box) space. Hint in creating a graph using Excel spreadsheet: To create/plot a graph of Potential vs. Current. (a) open an Excel spreadsheet, (b) type in the cells, current (Amp) for the first column and voltage or potential (Volt) for the second column and the corresponding data points, (c) highlight all entries, (d) click insert then click on insert scatter (X, Y) located above Charts at the middle top of the control panels, (e) on the drop-down menu that appears, click on the first selection composed of dots alone, (f) on the graph that appears, click on the title and edit to become Potential vs. Current Graph or Voltage vs. Current Graph, (g) right click on any of the plots or dots, (h) on the drop-down menu, select Add Trendline, (i) on the right side of the screen, the Format Trendline appears, select Linear, check off set-intercept to 0.0, check-off Display Equation on Chart, (j) on the graph, edit the equation that shows, change y to Voltage, x and change x to Current, (k) click on the “+” sign located at the top right corner of the graph, check-off Axis Titles, (l) click on the Axis Title at the bottom of the graph and change it to Current (Amp), (m) click on the Axis Title at the left side of the graph and change it to Voltage (Volt), (n) click the inside part of the graph then right click and select copy, (o) open this lab document and paste the graph below these instructions, (p) on Excel spreadsheet, highlight the all data points then right click and select copy, (q) on the lab document, paste the data table before or next to the graph, (r) edit all entries as needed. Piggyback to Lab 2 about graphing using Ohm’s Law Voltage (V) vs. Current (I) 9 f(x) = 287.25 x R² = 1 8 Voltage (Volts) 7 6 5 Voltage (V) Linear (Voltage (V)) 4 3 2 1 0 0 0.01 0.01 0.02 0.02 0.03 0.03 0.04 Current (Amps) 8) Determine the slope of this curve from the results of the graph. How does this slope relate with resistance? Slope = 171.08. We realize that the slope of voltage vs. current is equal to the constant resistance. In fewer words, the slope equals the value of the resistance. 9) If the value of resistance were 288 Ohms (or so) instead of 172 Ohms (or so), how will this slope change (stiffer or less stiff slope)? Why? If the value of resistance increases, as in this question, the slope will be stiffer. This because as we already stated, the slope is the same as the resistance. So if the resistance increases, the slope will get stiffer. C. Extend your understanding: 10) Which among the following connections is a (correct) series combination of cells? a) Ohm’s Law b) c) Letter a) is the correct series combination of cells. 11) What is wrong with option c in #10? Write your answer below. The wrong thing regarding option c) is that the batteries are not connected properly. Cells are joined end to end in a series connection. In other words, the positive terminal of a cell needs to be connected to the negative terminal of the next cell. And as the picture shows, the batteries are not following this pattern. 12) How do you call the cell combination in #10 b? The cell combination in option b) is called parallel circuit. In this particular circuit, a branched or multi-pathway is formed for the flow of electrons 13) If you need to make 9.0 Volt battery by using 1.5 Volt cells, how many minimum cells you will need? And how will you connect them? I will need 6 cells in order to make a 9.0 Volt battery with 1.5 volts cells. The way to connect them will be by using a series circuit. Ohm’s Law Post-Lab Questions: 1) Explain Ohm’s law, in your own words, but using the results of the lab activity. The Ohm’s law is a relationship between the current I, the resistance R, and the voltage V. And as we saw on the lab, the Ohm’s law can express with the formula I= V/R. Moreover, as we saw on the lab, we now know that the current is affected in direct proportion to the voltage, and inversely with the resistance. In other words, if the voltage increases the current also increases, and if the resistance decreases the current also decreases. 2) What is the relationship between the slope of the Voltage vs. Current graph and the resistance of the wire in the circuit? As seen on the graph made earlier, we conclude that the slope of the graph is equal to the constant resistance. In fewer words, the slope equals the value of the resistance. Slope = resistance. 3) Is the slope of the Voltage vs. Current graph constant? How do they call materials with constant resistance (slope)? What about those materials with non-constant resistance (slope)? The slope we obtained within the graph is in fact constant. This means that the materials with a constant slope (resistance) are called ohmic material. In the other hand, the materials that have a non-constant slope (resistance) are referred to as non-ohmic materials. 4) What is series connection? Parallel connection? A series connection is a single-pathway circuit for electron flow. The single-pathway is by connecting the positive terminal of a cell to the negative terminal of the next cell. Moving forward, the parallel connection is a branched or multi-pathway that is formed for the flow of electrons. Conclusions: Write a summary (explanations) of the physics concepts learned based from the results of the lab experiment. Elaborate. Provide real-life applications/examples. The Ohm’s law is the main concept regarding this lab. It shows the relationship between the current I, the resistance R, and the voltage V. And as we saw on the lab, the Ohm’s law can express with the formula I= V/R. But I can also be express as R = V / I and/or � = � × � Moreover, we arrived to the conclusion that if the voltage increases the current also increases, and if the resistance decreases the current also decreases. Going more deeply with the components of the Ohm’s law, we have the voltage. Voltage is also known as electric potential. It is the energy that a source provides to each unit of charge, and its unit of measurement is the volt. Following with resistance, it describes how well a circuit component resists the passage of electric current. In other words, resistance blocks or opposes the flow of electrons or it uses the energy of the electrons. Finally, we have the current. The current obtained is also referred as electric current. An electric current is the flow of electric charge or electrons that transports energy from one place to another. The electric current is measured in ampere, which is the rate of flow of 1 coulomb of charge per second or 6.25 billion electrons per second). And the electric current may be in Ohm’s Law an alternating current or direct current. A direct current, also called DC, charges flow in one direction only. And there are factors that affect the current in the DC, which are established in Ohm's Law. This Ohm’s Law can be seen in an electric circuit. An electric circuit is any closed path along which electrons can flow. Moreover, devices can be connected in two ways: in a series circuit or a parallel circuit. A series connection is a single-pathway circuit for electron flow. The single-pathway is made by connecting the positive terminal of a cell to the negative terminal of the next cell. And the parallel connection is a branched or multipathway that is formed for the flow of electrons. Lastly, we are surrounded by the Ohm’s law in our life. We may not see it directly with our eyes or comprehend it altogether, but we are interaction with it every day. Basically, every electronic device is made with either a simple or parallel circuit, and inside that circuit the Ohm’s Law is happening. Since the inside or our phones while charging, the inner wiring for lightning in our house, to everyday devices at home such as conventional fans and electrical warmers. All of these devices, and more, are making the Ohm’s Law.