P142L08_Lab_Report_Template_v20230325

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UIC Physics Department Physics 142 Laboratory Report Electromagnetic Induction Page 1 of 7 Electromagnetic Induction ሺExperimental Procedure and Data Analysisሻ Lab Section ሺDay & Timeሻ: ________________________________ Name: ________________________________________________________________________ Station#: ____________ Partner: ______________________________________________________________________ Initial Setup  Make sure that Pasco 750 Interface is ON ሺA green light-emitting diode ሺLEDሻ on the front panel will lightሻ, and Power Supply is OFF.  Check that the Magnetic Field sensor and Voltage sensor are plugged into Analog Channels A and B, respectively. If NOT, call your lab TA.  Check that Magnetic field sensor is attached to the cart and its RADIAL/AXIAL switch is set to AXIAL ሺ↡↡ሻ and RANGE SELECT switch is set to 1X Then, start the Capstone program. To set up the hardware,  Click on the Hardware Setup icon in the Tools palette. If the 750 interface is turned on and is communicating with the computer, this will bring a clickable picture of the front panel of the 750 interface.  Click on “Analog Channel A” and add the “Magnetic Field Sensor”  Click on “Analog Channel B” and add the “Voltage Sensor” Now, you can hide the “Hardware Setup” window by clicking on its icon.  Drag a “Digits” display icon to the central page, then click ൏Select Measurement൐, choose “Magnetic Field Strength ሺ1Xሻ ሺTሻ” and change the number style to “Scientific Notation” with 3 significant figures. To do so,  Click on the gear icon on the top menu of the “Digits” display, then click on “Numerical Format” and make the following changes:  Number Style to Scientific Notation  Number of Significant Figures to 3 and then click “OK”  Next, drag “Graph” display icon to the center page. Click ൏Select Measurement൐ on the y-axis and choose “Voltage, Ch B ሺVሻ”, then click ൏Select Measurement൐ on the x-axis and choose “Time ሺsሻ”.  Change the number style to “Scientific Notation” with 3 significant figures. To do so,  Click “Data Summary” icon on left side menu, then under “Voltage Sensor, Ch B” click “Voltage, Ch B ሺVሻ, and then click on “Properties” icon.  Click on “Numerical Format” and make the following changes:  Number Style to Scientific Notation  Number of Significant Figures to 3 and then click “OK” Now, you can close the “Data Summary” window by clicking on its icon and rearrange the voltage vs. time graph and magnetic field strength display any way you like.

UIC Physics Department Physics 142 Laboratory Report Electromagnetic Induction Page 2 of 7 Coil #1 must be attached to the gray PVC table through hole #6 via brass thumb screw with the washer between the base of the coil and table. Coil #2 must be attached to the gray PVC table through hole #5 via brass thumb screw with the washer between the base of the coil and table.  Align the coil #1 base to the x6 – x6 line with the connectors on the base facing towards you.  Align the coil #2 base to the x5 – x5 line with the connectors on the base facing towards you. Part 1. Induction with a Bar Magnet Let’s see what happens when a bar magnet is brought near a coil.  Plug the red and black leads of the Voltage sensor into the white left-hand side and the white center connector at the base of Coil #1, respectively. Note: Induced EMF will be quite small ሺdozen of millivoltsሻ, so it’s a good idea to make the range of values along the vertical scale  0.1 V. To change the scale along either the 𝑦 െ or 𝑥 െaxis, grab any nonzero number on the axis ሺmouse icon will changeሻ, and drag up or down ሺ𝑦 െaxisሻ or drag left or right ሺ𝑥 െaxisሻ.  Click the “Record” button the graph should display the induced EMF in the coil as a function of time. Take a couple of minutes to try a few experiments. Be creative – try moving the magnet close to the coil and back, moving it around, rotating it, etc. When you have a feel for how moving the magnet induces an EMF in the coil, click “Stop”. Let’s do some systematic tests with the coil and magnet 1.1. At a distance, point the “North” ሺredሻ end of the bar magnet toward the coil. Press “Record” and quickly move it closer to the plane of the coil. STOP moving just before the tip of the magnet is near the plane of the coil as shown in Figure 3. All this must be done in less than one second. Press “Stop” button when you are done. 1.2. In Figure 3, draw the magnetic field lines through the coil due to the bar magnet with the arrows indicating its directions. 1.3. What is happening to the magnetic flux through the coil as you move the “North” pole closer to the coil? _________________________________________________________________________________________________________________________ 1.4. Is the induced EMF positive or negative? Why? ________________________________________________________________ _________________________________________________________________________________________________________________________ 1.5. According to Lenz’s Law, the current induced in the coil will create a magnetic field that resists the change in flux. In Figure 3, draw the magnetic field lines ሺdashed linesሻ produced by the induced current with arrows indicating its direction. 1.6. In Figure 3, on the edge of the coil draw an arrow indicating the direction of the induced current. 1.7. In Figure 4, roughly sketch the induced voltage as a function of time you observed. Figure 4 Figure 3

UIC Physics Department Physics 142 Laboratory Report Electromagnetic Induction Page 3 of 7 1.8. Would the direction of the induced current correspond to a positive or negative voltage, as measured by the Voltage sensor? Hint: Look at the way the coil is wound ሺclockwise as viewed from the frontሻ and imagine that the coil is a battery, with current leaving the positive terminal. ________________________________________________________________________________ 1.9. Does your previous answer agree with your observation? ___________________________________________________ If NOT, go back over this argument carefully. It’s critical that you understand what just happened 1.10. When the magnet was stationary, what happened to the induced voltage? Explain your answer. _________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________ 1.11. Now, place the north pole of the magnet directly at the center of the coil, then press “Record”, and this time, move the magnet away from the plane of the coil, back toward you. Then, press “Stop” button when you are done. 1.12. In Figure 5, draw the magnetic field lines through the coil due to the bar magnet with the arrows indicating its directions. 1.13. What is happening to the magnetic flux through the coil as you move the “North” pole farther from the coil? ___________________________________________________________________________________ 1.14. Is the induced EMF positive or negative? Why? __________________ _________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________ 1.15. In Figure 5, draw the magnetic field lines ሺdashed linesሻ produced by the induced current with arrows indicating its direction. 1.16. In Figure 5, on edge of the coil draw the arrow idicating the direction of induced current. 1.17. In Figure 6, roughly sketch the induced voltage as a function of time you observed. 1.18. Would this direction of the induced current correspond to a positive or negative voltage, as measured by the Voltage sensor? Hint: Look at the way the coil is wound ሺclockwise as viewed from the frontሻ and imagine that the coil is battery, with current leaving the positive terminal. _________________________________________________________________________________________________________________________ 1.19. Does your previous answer agree with your observation? __________________________________________________ If NOT, go back over this argument carefully. It’s critical that you understand what just happened Figure 5 Figure 6

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UIC Physics Department Physics 142 Laboratory Report Electromagnetic Induction Page 4 of 7 Now, let’s repeat the same experiment with the south end of the magnet pointing at the coil. 1.20. Place the south pole of the magnet directly at the center of the coil, then press “Record”, and move the magnet away from the plane of the coil, back towards you. Then, press the “Stop” button when you are done. 1.21. In Figure 7, draw the magnetic field lines through the coil due to the bar magnet with the arrows indicating its directions. 1.22. What is happening to the magnetic flux through the coil as you move the “South” pole farther from the coil? ______________________________________________________________________________________ 1.23. Is the induced EMF positive or negative? Why? __________________________ ______________________________________________________________________________________ ______________________________________________________________________________________ ______________________________________________________________________________________ 1.24. In Figure 7, draw the magnetic field lines ሺusing dashed linesሻ produced by the induced current with arrows indicating its direction. 1.25. In Figure 7, on the edge of the coil draw an arrow indicating the direction of the induced current. 1.26. In Figure 8, roughly sketch the induced voltage as a function of time you observed. 1.27. Would the direction of the induced current correspond to a positive or negative voltage, as measured by the Voltage sensor? Hint: Look at the way the coil is wound ሺclockwise as viewed from the frontሻ and imagine that the coil is battery, with current leaving the positive terminal. _________________________________________________________________________________________________________________________ 1.28. Does your previous answer agree with your observation? __________________________________________________ Part 2. Rotating a coil in a Uniform Magnetic Field We just observed that changing magnetic flux through a closed loop creates an induced EMF in that loop. The magnetic flux can change either because the magnetic field changes, the area of the loop changes, or because the angle between the loop area and the magnetic field changes. In this part of the lab, we will place a small induction coil at a point midway between two 300-turn coils connected in series, as shown in Figure 9, creating a nearly uniform magnetic field at the small coil location near its center.  Make all the connections between the two 300-turn coils and DC Power Supply shown Figure 9. Figure 8 Figure 7 Figure 9

UIC Physics Department Physics 142 Laboratory Report Electromagnetic Induction Page 5 of 7 2.1. When the DC Power Supply is ON, the current will flow through the coils, and it will generate a nearly constant magnetic field at the location of the rotating coil. Which way will this field point? _________________________________ ሺtoward you/ away from youሻ Let’s start with a quantitative measurements of 𝐵.  Slide the straight track carefully through the coils and place it into the holes 7 and 8 on the gray table with the numerical scale facing to the right.  Place the Sensor Assembly on the track and align the wheel with 23.5 cm on the scale, check that the Magnetic Field sensor is set to “Axial” and “1X” and gently press the “TARE” button.  Turn the Coarse and Fine Voltage knobs all the way clockwise and the Coarse and Fine Current knobs all the way counterclockwise and turn the Power Supply ON. The Power Supply’s ammeter must show 0.0 A. Then slowly turn the current knob clockwise until current reads 0.30 A. For the next few steps DO NOT change the current value, otherwise you will need to repeat the measurements. 2.2. Click “Record” then write down the experimental value of the magnetic field strength, B ௘௫௣ , below. B ௘௫௣ ൌ ________________________ ሺTሻ  Remove the Sensor Assembly from the straight track and place it on top of the Power Supply. Then, detach the straight track, carefully remove the track from the gray table and place it near the left-hand side of the gray table.  Screw the Induction Motor into hole #22 on the gray table. The small induction coil should now be situated between the two 300-turn coils. Then, make all the connections needed between the Circuit Board, the Induction Motor and Voltage sensor ሺsee Figure 9ሻ.  Go to the Capstone’s Controls Palette at the bottom of the screen and change the sampling rate to 50 Hz. Then, make the range of values along the horizontal scale in the Voltage vs. time graph between 0 and 10 seconds.  Depress and hold the Circuit Board switch and click “Record”. After about 5-7 seconds click “Stop” and release the switch. The graph will appear showing the induced EMF in the small rotating coil as a function of time measured by the voltage sensor plugged into Channel A.  Turn the Coarse and Fine Current knobs all the way counterclockwise and turn Power Supply OFF. 2.3. We can recall Faraday’s law to help explain your observations. In our previous experiments, to induce an EMF in a coil, we were changing the magnetic flux by changing the magnitude of 𝐵. Now, 𝐵 is a constant. What is changing now? _________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________ The aim now is to find the magnitude of the magnetic field generated by two 300-turn coils at the location of the small rotating coil. We can use Faraday’s law and the results of our last experiment to find the magnetic field. To be able to compare the result of our calculations with our measurement of the B ௘௫௣ we need to use the average values of EMF, ℰ ௔௩௚ , and average magnetic flux, Φ ௔௩௚ to get the theoretical value of the magnetic field strength ሺbased of Faraday Lawሻ, B ௖௢௜௟ , at the location of the rotating coil.

UIC Physics Department Physics 142 Laboratory Report Electromagnetic Induction Page 6 of 7 2.4. First, use the “Smart Tool” from the menu above the graph to measure the maximum value of the induced EMF. Record its value below. Max. induced EMF, ℰ ௠௔௫ ൌ ______________ ሺVሻ 2.5. Measure the length of ¼ cycle of the sinusoidal pattern, ∆𝑡 ଵ/ସ் . Hint: Use the “Smart Tool” to measure the time interval between adjacent maxima of the EMF and then divide the result by 4. Record the obtained value below. ¼ period, ∆𝑡 ଵ/ସ் ൌ ______________ ሺsሻ Note: Some important info about the rotating coil: Its diameter is 7 cm and it has 3000 turns. 2.6. Calculate the coil’s area: 𝐴 ൌ ______________ ሺm 2 ሻ 2.7. Calculate the average induced EMF: ℰ ௔௩௚ ൌ ℰ ௠௔௫ 〈cos 𝑥〉 ൌ ______________ ሺVሻ, where 〈cos 𝑥〉 ൌ ଶ గ ൌ 0.637. 2.8. Calculate the change in flux through the small coil using ℰ ௔௩௚ ൌ ቚ ௗ஍ ௗ௧ ቚ: ∆Φ ൌ ______________ ሺT  m 2 ሻ 2.9. Find the change in flux through a single loop of wire in the coil: ∆Φ ௟௢௢௣ ൌ ______________ ሺT  m 2 ሻ 2.10. In the time interval, ∆𝑡, the flux changes from 0 to maximum value, Φ ௠௔௫ ൌ 𝐵𝐴. This means that Φ ௠௔௫ ൌ ∆Φ ௟௢௢௣ . Therefore, use the value of ∆Φ ௟௢௢௣ obtained in previous step to calculate the magnetic field in the middle between the 300-turn coils: B ௖௢௜௟ ൌ ________________________ ሺTሻ  Remove all connections from the Induction Motor, detach it from gray table and put it back on the shelf. 2.11. Calculate the percentage difference between the two values of the strength of magnetic field generated by two 300-turn coils at midpoint between them, predicted B ௖௢௜௟ ሺin step 2.10ሻ and measured B ௘௫௣ ሺin step 2.2ሻ. _________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________ 2.12. If your % difference is greater than 20%, double check your calculations ሺsteps 2.4 – 2.10ሻ. What do you think are some possible sources of this difference ሺexcept “Human error”ሻ? _________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________________

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UIC Physics Department Physics 142 Laboratory Report Electromagnetic Induction Page 7 of 7 Cleaning up When you finish the lab, please unplug the 48” and 24” cables. Place the cables on center lab table and leave the rest equipment the same way as shown in the figure to the right. Otherwise, up to 8 points will be deducted from your lab score!

P142L08_Lab_Report_Template_v20230325

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