Physics Lab Report

Lab Experiment

Hi. Today we'll do this is [? Circuit ?] [? Two, ?] Kirchhoff's rules, electric power lab using virtual website from the KET website. Objectives of the lab. Objectives are to test Kirchhoff's voltage a nd current rules in the simulated complex circuit, to find the condition for a maximu m power transferred from a source to the load in a simple virtual DC circuit. The equipme nt, a computer with internet access. And we will use virtual labs from KET website. Please visit KET website. Use your username and password and log in. Then go to tab Labs. And select 16, DC Circuits lab from the list. Before running the simulation, read the ful l description and detailed information. OK. Now let's run the DC Circuit lab. OK. Now from the from the Pick a Circuit option , select Diagram.Pick a Circuit option is here. Click this row. And click down to select Diagram. And adjust the values of the circuit elements as shown below in the picture. If you cannot see the value of the element in your lab manual, you can zoom the picture to see it or I can tell you R1which is-- this is my R1. R1 is 10 ohms. R2 is on the right side. This is my R2. It is 10 ohms as well. And R3 is a diagonal one. And R 3 is 20ohms. Connect 10 ohms on the right side, 10 ohms on the left side. And on the diagonal is 20ohms. And the battery is here if you need to adjust these values. OK. Now let's click on this one and adjust the R1. This is my R1. It's 10 ohms. Now click on the second one. This is 10 ohms, again. If you click here, it shows resistance of 5. Now you need to adjust it to20 ohms. Enter. Now I have 20 here and 10 on each side. Now adjust the batteries. The upper one, which is V1,adjust this battery to voltage 30 volts. It must be 30 volts. And the lower battery adjusts to 5 volts.Good. Now we have all the parameters adjusted. V1 is 30 volts. V2 is 5 volts. R1 is 10 ohms. R2 is 10ohms. And R3 is 20 ohms. As you can see, your circuit has two junctions which is junction A-- this is my junction A-- where the current is splitting, and junction B. Two junctions. These are not junctions. Pay attention. The same current is going through this wire or the other wire. Only we have two junctions, one and two. Now connect virtual ohmmeters, of course, in series. You remember, [? the ?] [? ohmmeter ?] must be connected in

a series. With circuit components and voltmeters, they should be connected in parallel with circuit components as necessary to test the Kirchhoff's current law for junction B. We checked the currents law for junction B and Kirchhoff's voltage law for both loops. OK. We can connect ohmmeters. OK. To connect ohmmeter, click on ohmmeter. Let m e open the circuit first. I want to put on the ohmmeter between these two. [? Rerouting ?] the current and [? diagonal. ?] OK. This is now the value of the current. Now I want to put another ohmmeter. Let's see. Let's put it here. I am opening the circuit. I will bring the ohmmeter here. Over a little bit. Up. Connect the ohmmeter terminal to the circuit to close the loop. 5. This is 30. This is 10. This is 20. This is 10.Correct. And we need to put one more ohmmeter. Let's put another ohmmeter. I can put another ohmmeter here. OK. I connect the ohmmeters-- three ohmmeters-- to show this current, another current,and this current. And you see there is one with a positive sign. The others are with a negative sign.OK. Now connect voltmeters to [? measure ?] the loop [INAUDIBLE] for both loops. The first voltmeter, Iconnect on the battery, wh ich shows 5 volts. This is the ohmmeter. Voltmeter, I have to connect here now to show voltage [? drop ?] on this resistor. And voltmeter, I want to connect on this resistor. And for the second loop as well. Here is my-- on the battery on top. And the voltmeter,we put here. OK. This is what do you need to do. Connect your ohmmeters and voltmeters on [INAUDIB LE] to check Kirchhoff's rules for the junction B. That is the junction rule that you have to prov e that the current coming in the junction must be equal to the current going out from the junction. And loop rules that the sum of the voltage is across each element around any clos ed loop must be0. For this loop, that is loop 2, and for the loop 1 also, the sum of th e voltages should be 0. And you have a sample in your manual. But pay attention that in this example that the parameters are different than what you need to measure in your experiment. Part two, electric power in a DC circuit. Start a new simulation in DC Circuit lab in the virtual physics lab environment. Set up the circuit shown in your lab manual. You need a battery. Connect the battery. Resistor to the battery-- connect the resistor to the battery. Then we will adjust the parameters. And then, let's put one wire. One more wire-- I want to do exactly what you see there.Ohmmeter, we have to connect here.

Now we need to connect a voltmeter parallel to the resistor. We can do it that way or we can do extra wires as you can see in your lab manual. By double- clicking the switch, you will close the circuit, and we will have a current. You double-click one more time, it will open the circuit. Now let's adjust the parameters. [? So ?] we'll adjust the voltage of the battery. 10 volts-- we have already 10 volts here. Now adjust the resistance. This is the resistance. All right. Which is here, the internal resistance. You put that specific resistor as internal resistance. And it mu st be 15 ohms. It already is 15 ohms. Now adjust this one for the beginning. These are load resistors. Load resistors sho uld be 0.5.Initial value of the load resistance, adjust to 0.5. And click Enter. We adj usted all the parameters.Now we are trying to see at which value of the load resistance we will get maximum dissipated power on the load resistor. In other words, we will start changing the load resistors and measure the current and voltage for each value of the load resistor, and calculate the power dissipated on that load resistor, and make [? graph ?] power versus the value of the load resistance. And you will see that [? graph ?] has a maximum value and specifically that maximum will happen when the load resistance will be equal to the internal resistance. Now you need to open LoggerPro. Logger Pro, go open Logger Pro. And in Logger Pro, you need to create columns R load. The first column you creat e, call it RL. I will call it RL, R load. And the second one, the unit will be ohms. [? Shorten ?] [? it. ?] RL again. Unit will be ohms. And name the second column as current. Our unit will be ohms. You need to creat e one extra column. New Manual Column. And create that column and label it V, Voltage. VL. [? Just a bit. ?]And unit will be volts. And you need to create one more calculated column. Go to Data and create New CalculatedColumn, which we will name Power. Short name, P and unit for the power-- remember, the unit for the power is watt. And how to define that power? That power you will select Varia bles. FromVariables, you can write Current. Multiply voltage. OK. Now you have all columns created. Let me make this a little bit smaller to see all columns over there. Yeah. We adjust the width of the columns to see all of the columns. Now you are ready to collect the data as described in step 1 through 3 in your lab manual. Step 1,in the simulation circuit, close the switch, double- clicking on the switch. And record the current

and voltage displayed by measuring instruments. Here's our switch. Double- click on the switch. We will see the current is 0.65 amps and voltage is 0.32 volts. Take these ratings and enter into Logger Pro. Automatically power will be calcula ted. Here is what was my load resistors. It still is a small value. That was 0.05.-- 0.5. And current was-- just read the values and let me write it down-- 0.65 ohms. And voltage is 0.32 volts. Come back here. 0.65and 0.32. OK. Right away, power will be calculated in watts. And the dot appears on your graph. Now, go back again to your circuit. Double-click on the switch. Open the circuit. With the left click, select the load resistor and change its value in the Resistance window to a new value. Repea t step 1 to 3while changing the load resistor by 2 ohms in the range of 2 ohms to 18 ohms. OK. Now let's change the load resistor. Here is my load resistor. We need to put 2 ohms. Just you highlight and type. And this is now 2 ohms. And double-click the switch to close it. Now the current is 0.59 and 1.18 volts. Enter this data in Logger Pro. That is now 2 ohms. And you get 0.59 and 1.18. You g et another point. Continue your experiment. Now we need to open the circuit, change the resistor. Click on the resistor. And no w go to 4 ohms.Enter. Click to close. You get 0.54 And 2.11 volts. Enter this point in Logger Pro. You can read all the data and then enter the data in Logger Pro. 0.53-- sorry, that is 4 ohms. 4 ohms. It's 0.53 and2.11. On the y-axis, now, I have current. I need to replace that. I need to change it to power. It must be my power. OK? Power in watts. And continue doing this as it's described in your la b manual. And then, when you get all the data points, you need to fit the graph by the function. Again, it's provided in the lab manual. Instead of parameters V and R [? arrays, ?] you can put a and b parameters to make it easy to fit the graph with the function. And then, from fitt ing parameters,you can see that the maximum will happen when your load resisto r is equal to your internal resistors. You can double-click on the legend of the [? fitting ?] [? parameter ?] box to get the errors as well.Just follow the instructions. It is very eas y to follow. And if you will have questions during the experiment time, you can contact us. Thank you.