Lab #1 Help Document. This lab will be completed in room 335 CTB. You will need to partner up for this lab in groups of two.

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1 Lab #1 Help Document This help document will be structured as a walk-through of the lab. We will include instructions about how to write the report throughout this help document. This lab will be completed in room 335 CTB. You will need to partner up for this lab in groups of two. This lab will require the use of the following pieces of equipment: DC power supply DMM

2 Bread Board 5 Resistors: Resistance Value in ohms (Ω) Color Bands 33 Ω Orange-orange-black 100 Ω Brown-black-brown 330 Ω Orange-orange-brown 1.0 k Ω Brown-black-red 3.3 k Ω Orange-orange-red There are 7 steps in this lab. It is best for this lab to do them in the order that they are written. 1. First measure the resistance of each of your resistors using the DMM. Determine how close it is to its rated value, and whether it is within its rated tolerance. For this part of the lab, you ll be measuring the values of the 5 resistors using the DMM. The breadboard will be used throughout the lab to hold and connect the resistors. Before you can measure the values of your resistors, you will need to configure your DMM (Digital Multimeter) to make resistance measurements. What follows is an explanation of how to configure the DMM for making certain types of measurements:

3 How to use the DMM There are 4 holes located in the upper left corner of the DMM. The red and black leads are inserted here. The configuration of the leads depends on the measurement you are taking. When measuring voltage and resistance, the DMM needs to have its leads configured in the following manner. The black lead needs to be inserted in the bottom left hole labeled COM. The red lead needs to be inserted in the upper left hole labeled with a V and Ω (Omega symbol).

4 When measuring current, the DMM needs to have the black lead inserted in the bottom left hole labeled COM and the red lead inserted in either the top right (labeled 10 A) or bottom right (labeled 100 ma) hole. Unless the lab requires that 10 or more Amps of power be measured (which is usually not the case), assume that for measuring current the red lead will always be inserted in the bottom right hole labeled 100 ma. There are 5 buttons located beneath the display that activate different measurement settings. The top three from left to right are DC Voltage, DC Current, and Resistance. The bottom two buttons are AC Voltage and AC Current. After configuring the leads, you must select the setting by pressing its respective button if you want to correctly measure anything.

5 The DMM has the ability to automatically adjust its unit resolution. To enable this ability, the word AUTO must be shown in the top right corner of the display. If this is not the case, press the grey button labeled AUTO which is the second button down located beneath the display. If AUTO is not active, some of your measurements may yield an O.L on the screen. This stands for OVERLOAD and happens when the measurement is too big to be accommodated by the screen on its current unit resolution setting. You can manually adjust the unit resolution by pressing the grey up and down arrow buttons located beneath the display.

6 Back to Step 1 Based on the information you just read, you will need to place the red lead in the V/ Ω hole (upper left) and the black lead in the COM hole (lower left). You will also need to press the Ω button located beneath the DMM display and ensure that the DMM is set to AUTO so that it automatically adjusts the units. To measure the value across the resistors, place the one you are measuring in the breadboard. It is better to do this than to hold the DMM leads on both ends of the resistor since your body has a resistance and the reading you get will be the resistance for your resistor and your body being connected in parallel. ORIENTATION ON THE BREAD BOARD IS IMPORTANT! What follows is an explanation of how to properly place resistors on a breadboard: How to use a bread board A breadboard is a device that allows you to make circuits without soldering the leads. The breadboards used in this lab have 3 sets of connections composed of columns of connection holes. The first set is in columns of two holes. The second and third sets both contain columns of five holes. The sets do not connect to each other so connections made between sets are okay. Rows are not connected to each other along their holes while columns are. In other words, all holes within a column are connected together while all holes within a row are independent. Because of this, you NEVER place a component like a resistor such that two or more of its leads are in the same column. This will create a short circuit and can burn out the power supply. You can place one lead each from different components in the same column to connect them. For example, you can place one lead from a 100 ohm resistor and one lead from a 330 ohm resistor in the same column in order to connect them. If their other leads connect to differing columns, the resistors will be connected in series. If their other leads connect in the same column, the resistors are connected in parallel.

7 Back to Step 1 Based on the instructions above, you will need to place the resistors in the breadboard by placing both leads in the same row, but in different columns. THIS IS VERY IMPORTANT! Current takes the path of least resistance. If both leads are in the same set and the same column, the test current being generated by the DMM will go through the bread board wiring instead of the resistor because it has less resistance. The result is a short circuit which at best will give you a wrong reading and at worst will blow the DMM s fuse rendering it unusable until the fuse is replaced. To measure the resistance across each resistor, simply place the black lead of the DMM on one of the resistors leads and the red lead on the other as shown below.

8 The reading on the display is your resistance. Take care to note the units that the display is using. Just the Ω symbol means ohms, k Ω means kilohms (1,000 ohms), and M Ω means megohms (1,000,000 ohms). Note: If the DMM number reading keeps changing, just pick one that shows up a lot. If the reading continues to steadily increase or decrease, use the first reading before it begins to decrease/increase steadily. The next part of step 1 is to determine how far the measured values you got are from the rated values (known as percent difference) and whether or not your resistors are within tolerance. To determine the percent difference between your measured and rated resistance values, use the following formula: [(MV RV)/RV] * 100 where MV = Measured Value RV = Rated Value To determine if your resistors are within tolerance, look at the 4 th band after the first 3. This band will either be a gold band, silver band, or no band. Gold means the tolerance is +-5%. Silver means the tolerance is +-10%. No band (only 3 instead of 4 on the resistor) means that the tolerance is +-20%. Example, if your resistor has a gold band and your calculated percent difference is -3.45%, then your resistor is within tolerance. If you calculated 6.78%, then your resistor is out of tolerance. Lab Report For your lab report, you will need to record the steps you took to measure the resistors, the resistances that you measured, the percent difference equation and its components, your calculated percent difference values, and whether or not the resistors were within tolerance. Be sure to specify the units with all resistance values. You can use pictures to describe how you made measurements. For example, to describe how you set up the DMM you can say: I configured the DMM to make voltage measurements, and follow that with a picture or diagram of the DMM showing the red and black leads in the proper holes along with the screen on showing the units for resistance. Then for the actual measurements, you could say something like: Measurements were taken as shown in this picture/diagram, and then have a picture showing a resistor on a breadboard with the red lead of the DMM on one side and the black lead on the other. You could also use a written description, though image descriptions may be simpler to create especially if pictures are taken of the steps during the lab process. Regardless of whether you use images or written descriptions, ensure that the description is complete, meaning another person who hasn t taken this lab and doesn t know how to set up the equipment could use your description to make the same measurements. Also, keep digital copies of this and future lab reports in case the same measurement is made during a future lab. You can use the descriptions from this lab for those reports as well as long as they don t have extra bits that need to be documented.

9 If measurements are made multiple times during a lab, you only have to describe the first measurement with the detail indicated above. All other measurements of the same type can refer to this description. For example, if you measure resistance in part 1 and part 6, you only have to describe the method of making the measurements and setting up the DMM in part 1. You can refer back to them in part 6. You do still need to include any measured values however for both parts. As far as recording your data is concerned, include the following information: Include all used equations. This part of the lab only had one, so include it: [(MV RV)/RV] * 100 where MV = Measured Value RV = Rated Value As with measurement descriptions, equations that are used more than once in the lab do not need to be double stated. State the equation in the lab report where it occurs first and refer back to it for later parts of the lab. Remember that you do still need to include calculated values for both parts. Organizing data in a table format makes it easy to read so, while it is not a requirement, it is a recommendation. Be sure to label the data accordingly and include the units (if any). If the units aren t included in the label or if you aren t using a table to show your data, then each number will require its respective units to be included with it. If the units aren t shown in a way that clearly indicates which numbers they belong to, then as TA's we can't be sure what the numbers are for so you will lose some credit. Rated Value (ohms) Measured Value (ohms) Calculated % difference Tolerance of resistor (%) Is it within tolerance? No Yes Yes 1, Yes 3,300 3, Yes After you have checked your resistors to ensure that they are within tolerance and are the correct values, do the following to observe the relationships described by Ohm's law: 2. Set the DC power supply to a voltage between +3V and +5V; be sure to record the voltage you Since this is likely your first time using these DC power supplies, let's go over some brief setup instructions to ensure the proper function of the power supply. How to use the DC Power Supply The DC Power Supply has three power outputs. The two left-most have 3 output connections (black, green, and red) and are for the variable supplies which are controlled with the current and voltage knobs. The right most output (only has black and red connectors) is for a fixed 5V 3A supply of power.

10 We will be using the middle output set for this lab. The proper configuration of the DC Power supply for this lab is as follows. Make sure both of the buttons in the middle of the device between the two variable supplies are out not in (set to independent). Make sure that your black lead is connected to the green connector of the middle output and that your red lead is connected to the red connector of the middle output. Also, make sure that there is either a wire or a metal bar connecting the black and green connectors together. If there is not a connection between the green and black connectors and/or if the green is connected instead to the red connector, disconnect the red and green connectors and then connect the green and black connectors.

11 Before use, you must also turn the rightmost current knob greater than half-way up and turn the rightmost voltage knob such that the output voltage is the value indicated by the lab exercise. Back to Step 2 Once you've ensured that your DC power supply is set up as indicated by the above instructions, turn the right-most knob for voltage until it's output reads between 3 and 5 volts. Lab Report For this part on your lab report, all you need to do is state that you, set the DC power supply to output a voltage of x, where x is the voltage you set. For example, a voltage of 4.8V. 3. Measure the current through the circuit with each resistor, in turn, connected (one at a time) to the power supply. Determine how close the actual (measured) current is to the current predicted by Ohm's law. Draw a graph of the actual results compared to the predicted results. Determine the percent difference for each measurement. For this part of the lab, you will first place each resistor, one at a time, on the breadboard and measure the current going through it. To measure current, follow the procedure described below: Measuring Current Through a Resistor To measure the DC current through a resistor, you will need the DMM and the DC Power supply. First, if you haven't already done so, make sure that the DC power supply is correctly configured and set the voltage to the value indicated in the lab using the rightmost voltage knob (step 2 of the lab). Also configure the DMM for DC current measurement by placing the leads in the correct holes and selecting the DC current (not AC current) setting.

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13 Connect the black leads of the DMM and the DC Power Supply together. Then connect the red lead of the DC Power supply to one lead of the resistor and the red lead from the DMM to the other lead of the resistor. This configuration places the DMM in series with the resistor allowing it to measure current. Back to Step 3 After making and recording the current measurements for the 5 resistors, calculate the current you would expect to get from your set voltage using ohm's law: I = V/R where I = current in amps V = voltage in volts R = resistance in ohms (use the rated resistance value of the resistor, not the one you measured earlier in part 1 of the lab). BE CAREFUL HERE! The DMM will likely make the measurements in millamps, not amps, if it is set to AUTO. Be sure to make appropriate conversions before comparing between these measured results and the calculated ones (1 amp = 1,000 millamps). Take the measured and calculated values and graph them. Microsoft Excel can be used for this and the graph inserted into your lab report. Now take the measured and calculated current values and determine the percent difference between the measured and expected values using the percent difference equation with the following variables: [(MC CC)/CC] * 100 where MC = Measured Current CC = Calculated Current

14 Lab Report For your lab report for this step, you will need to record the steps you took to measure the current through the resistors, your measured values for current through the 5 resistors, your calculated expected current values, the graph comparing measured to calculated current values, and the percent difference values. Be sure to specify the units with all current values (amps). You can use pictures to describe how you made measurements. For example, for setting up the DMM you can say: I configured the DMM to make current measurements, and follow that with a picture or diagram of the DMM showing the red and black leads in the proper holes along with the screen on showing units for current. Then for the actual measurements, you could say something like: Measurements were taken as shown in this picture/diagram, and then have a picture showing a resistor on a breadboard with the red lead of the DMM on one side, the red lead of the DC power supply on the other side of the resistor, and the black leads connected together. You could also use a written description, though image descriptions may be simpler to create especially if pictures are taken of the steps during the lab process. Regardless of whether you use images or written descriptions, ensure that the description is complete, meaning another person who hasn t taken this lab and doesn t know how to set up the equipment could use your descriptions to take the same measurements. Also, keep digital copies of this and future lab reports in case the same measurement is made during a future lab. You can use the descriptions from this lab for those reports as well as long as they don t have extra bits that need to be documented. As far as recording your data is concerned, include the following information: Include all used equations. This part of the lab had two: ohms law and the percent difference equation, so include: I = V/R where I = current in amps V = voltage in volts R = resistance in ohms And (you don t have to include the % difference equation since you used it before, however you do need to at least refer to the equation you reported in part 1 of the lab. Say something like, used % difference equation from part one to calculate the following results. Be sure to include the numbers you used for calculation as well as the answers you got as well as the units of all of those numbers.) [(MC CC)/CC] * 100 where MC = Measured Current CC = Calculated Current Include the graph that you made that compares the measured to the expected currents.

15 Series 1 is for measured values Series 2 is for calculated values (be sure to label or identify which series is which. Without that, your TA s can t tell and you will lose some credit.) Organizing data in a table format makes it easy to read. Be sure to label the data accordingly and include the units (if any). If the units aren t included in the label, then each number will require its respective units to be included with it. If this isn't done one of the two ways mentioned above, then as TA's we can't be sure what the numbers are for so you will lose some credit. (In this case, units are likely to be in millamps or thousandths of an amp). Based on a voltage of 4.8V Resistor value (ohms) Measured Value Calculated Value Calculated % difference (millamps) (millamps) , , Decrease the voltage by 1 Volt and repeat the procedure above. Did the current go up or down? Were the results as you would have expected? This part is pretty self-explanatory. Simply reduce the voltage by 1 volt and repeat the same procedures for measuring current, calculating expected current, graph the new measured and calculated currents, and calculate the percent differences between the new measured and calculated currents.

16 Lab Report For your lab report for this step, you do not need to explain how you made measurements since they are the same steps that you used above. You do need to state that you reduce the voltage by 1 volt to x (your new voltage which needs to be included here as well) and you need to state all measurements, calculated values, graphs, and other data that part 3 required you to make. Example Voltage of 3.8V (which is 1 volt less than the previous example voltage of 4.8V). This step of the lab also asks you if the current went up or down and if these results are what you expected. State whether the current went up or down from step 3 to step 4 and if that is what you expected to happen. Explain why you did or did not expect the increase or decrease in current. As far as recording your data is concerned, include the following information: Include all used formulas. This part of the lab had two: ohms law and the percent difference equation, so include: I = V/R where I = current in amps V = voltage in volts R = resistance in ohms and [(MC CC)/CC] * 100 where MC = Measured Current CC = Calculated Current Include the graph that you made that compares the new measured and expected currents. Also remember to label or specify which line is measured current and which is calculated. Remember to label your data and include the units (if any). If the units aren t included in the label, then each number will require its respective units to be included with it. If this isn't done one of the two ways mentioned above, then as TA's we can't be sure what the numbers are for so you will lose some credit. Based on a voltage of 3.8V Resistor value (ohms) Measured Value Calculated Value Calculated % difference (millamps) (millamps) 33 xxxx xxxx xxxx 100 xxxx xxxx xxxx 330 xxxx xxxx xxxx 1,000 xxxx xxxx xxxx 3,300 xxxx xxxx xxxx

17 To observe the effects of combining resistors in series, do the following: 5. Set the DC power supply to +5V; connect a 330Ω resistor and measure the current. For this part, set the power supply to 5V. Then place a 330 ohm resistor on your breadboard and measure the current going through it. If you need some help with this part, refer to step 3's instructions on using the DC power supply and measuring current. Lab Report For this part of the lab report, you need to state that you set the DC power supply to +5V DC. You also need to state that you measured the current through the 330 ohm resistor using steps that you described earlier in the report (again, you don't have to double record how you make a measurement within the same report if you've done it before. Simply refer to it when you state that you made the measurement). Also state the value of the current that you measured through the 330 ohm resistor. 6. Now add a 1.0kΩ resistor in series with the 330Ω resistor and measure the current. Did the current go up or down? Calculate the expected current for the series combination, and compare this value to the measured current. Were the results as expected? For this part of the lab, you first need to add a 1kohm resistor in series with the 330 ohm resistor. Please refer back to step 1 s breadboard diagrams if you need some help with this. Now, measure the current across both resistors. This works the same was as with only one resistor except that the red lead from the DMM is on the open end of one resistor and the red lead from the DV Power supply is on the open end of the other resistor. DON T connect either red lead in the center between the two resistors. This will give you an incorrect reading. Next, you need to calculate the expected current you would get from this resistor circuit. To do that, you need to find the total resistance and then use that as the resistance value in ohm s law. To find total resistance in a series circuit, you would use the following equation: Rt = R1 + R2 + R3 + where Rt = Total Resistance R1 = Resistance of first resistor (use rated values not measured values for these) R2 = Resistance of second resistor R3 = Resistance of third resistor Since you only have 2 resistors, you would only need Rt = R1 + R2. Next, you would plug that into I = V/R where R would be equal to Rt.

18 Lab Report For this part of the lab report, you need to state that you added a 1kohm resistor in series with the 330 ohm resistor. You need to state whether the current went up or down from the current through just the 330 ohm resistor in step 5. You need to show your calculations for the current through both resistors and your comparison of the calculated vs. the measured values (this can be a written comparison). You need to state if the results were expected or not and why. For data, include the formulas you used: Rt = R1 + R2 + R3 + where Rt = Total Resistance R1 = Resistance of first resistor (use rated values not measured values for these) R2 = Resistance of second resistor R3 = Resistance of third resistor and I = V/R where I = current in amps V = voltage in volts R = resistance in ohms Also remember to include your measured and calculated current values. 7. Now add a 100Ω resistor in series with the other two. Measure the voltage drop across each resistor and compare to what you would expect using the voltage divider rule. Does the sum of the voltage drops equal the applied voltage? Would you expect it to? For this part of the lab, first connect a 100 ohm resistor in series with the 330 and 1,000 ohm resistors. Next, you ll need to set up the DMM to make DC voltage measurements and then measure the voltage drops across each individual resistor. Instructions on how to do this are provided below: How to measure the voltage drop across resistors that are in series To measure the voltage drop across a resistor that is in series with other resistors or components, you will need the DMM and the DC Power supply. First, make sure that the DC power supply is correctly configured and set the voltage to the value indicated in the lab using the rightmost voltage knob. Also configure the DMM for DC voltage measurement by placing the leads in the correct holes and selecting the DC voltage (not AC voltage) setting.

19 Connect the red lead from the DC power supply to one end of the circuit and the black lead to the other. In order to measure the voltage drop across a single resistor, place the red lead and black leads of the DMM on opposite sides of the resistor being measured such that the red lead of the DMM is closest to the red lead from the DC power supply and the black lead of the DMM is closest to the black lead of the DC power supply.

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21 The voltage shown on the DMM display is the voltage drop across that resistor. To measure the voltage drop across another resistor, simply connect the DMM leads to that resistor in the same way that you did to the first.

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23 Back to Part 7 Next, you ll need to use the voltage divider rule to calculate the expected voltage drops across those 3 resistors. The instructions for how to do that are as follows: How to Calculate Voltage Drop across a Series Circuit To calculate voltage drop across a resistor in a series circuit, use the following equation: Vout = Vin * ( Ri / (R1 + R2 + R3 + )) where Vout = the voltage drop of the resistor Vin = the input voltage from the power supply Ri = the resistance of the resistor (as printed on the resistor) (R1 + R2 + R3 + ) = the total resistance of the series circuit For example, if we had a series circuit with three resistors: R1= 100 ohm, R2= 200ohm, R3= 300ohm and the voltage input was 4V, the equation for finding the voltage drop across R1 would be set up like this: Vout = 4V * (100 / ( )) which gives us 0.666V Back to Part 7 After calculating the expected voltage drops, answer these questions: Does the sum of the voltage drops equal the applied voltage? Would you expect it to? Lab Report For the lab report, you need to explain how you measured the voltage drops across each resistor. Again, this can be done with a picture(s) or with a written description. Whichever you choose is okay as long as it describes completely how the DMM was set up, how the Power Supply was connected to the circuit, and how you applied the DMM to the circuit to make measurements. Include your measured values for each resistor as well as their added value. Remember to include the units, which should be volts in this case. Include a copy of the voltage drop equation and it s component parts. Vout = Vin * ( Ri / (R1 + R2 + R3 + )) where Vout = the voltage drop of the resistor Vin = the input voltage from the power supply Ri = the resistance of the resistor (as printed on the resistor)

24 (R1 + R2 + R3 + ) = the total resistance of the series circuit Include your calculated expected voltage values and their units. Answer the following questions about your measured values based on the results from the calculated values: Does the sum of the voltage drops equal the applied voltage? (refers to your measured voltage drops) Would you expect it to? (hint, reference the calculated voltage drops. How do they compare to measured?) Report and Conclusion Tell what this lab has taught or reinforced. Include "small" things, like how to connect an electronic circuit, a DMM, draw a schematic, etc. Lab Report If you haven t been doing this, state observations and results of the lab in the reports section along with any questions that the lab asks you to answer. It would be helpful if you numbered the results according to which part of the lab they are from if you record your results this way. Use the conclusion section to include any conclusions drawn, personal observations, or other things you wish to note about the lab. If you ve been including the observations and results as you go, you only need to write a conclusion which includes any conclusions drawn, personal observations, or other things you wish to note about the lab. Also, if a lab asks specific questions in the conclusion, answer them here. This particular lab does not, so don t worry about that here. Equipment State all pieces of equipment used, their manufacturers, and their serial numbers (or model numbers). A picture can be used for this as well as long as it captures the necessary information. List all equipment that is included at the top of this help document. Components like resistors do not require model numbers or manufacturers. Simply state 33 ohm resistor, 100ohm resistor etc. or show a picture of all 5 (needs to be a clear picture). You can also use the resistor table included in the help document for this. Other parts of the Lab Report Make sure that you include the following parts at the top of your lab report if you haven t done so already: 1. NAME and DATE: Put your name and the date of completion on the first page of the lab report. 2. LAB # and TITLE: Write a short, descriptive title for the lab. This should be on EACH page of the report. 3. OBJECTIVE: Write a statement that will explain what you are setting out to do.