PHYS 212 - Online Lab 3: Electromagnetic Induction Objectives: The purpose of this experiment is to investigate Faraday's law of induction and how an electrical potential (voltage) is generated in a coil of wire by a changing magnetic flux. We will also investigate how an electrical current-carrying coil of wire creates a magnetic field, that when changing, can induce an electrical potential and current in a neighboring coil. Equipment: Computer PhET Faraday's Electromagnetic Lab Simulation Software Theory: The principle of electromagnetic induction is one of the most technologically important and is the basis for much of our modern civilization through its application in generating and transmitting electrical energy. All electrical energy resulting from hydroelectric (water), coal, oil, gas, and nuclear-fueled Power Plants use electromagnetic induction, as well as does wind power. (Only solar electrical energy generation is different and uses the "photoelectric effect" to convert rays of sunlight directly into electrical energy.) Electromagnetic induction creates an electrical potential in a coil of electrically conductive wire when the magnetic flux passing through the wire coil changes with time. The magnetic flux @ is the number of magnetic field lines passing through the wire coil and is defined mathematically as the total magnetic field B through a loop of wire with cross sectional area A multiplied by the angle @ between the normal to the plane of the loop and the magnetic field direction (Equation 1): = B . A = BA cos 0 (1) Where the unit of magnetic flux is the Weber (Wb), which is equal to T.m' or V.s. According to Faraday's Law of Induction, a changing magnetic flux through the coil induces a voltage or an electromotive force (emf) in the coil (Equation 2): E = -N (2) AtWhere: & is the induced voltage or emi N is the number of turns of wire in the coil 8 is the magnetic flux through the coil is time in units of seconds . In this experiment, we will use these equations for magnetic flux (Equation 1) and Faraday's Law of Induction (Equation 2) as "design" equations. We will explore the effect on the induced voltage as a function of changing the key variables of: magnetic field strength B, coil area A, number of loops of wire in the coil (N), and the rate that the magnetic flux is changed in the coil with time. . Note also by Ohm's Law, an induced voltage or emf across a resistor will lead to an induced current (Equation 3): ind = Gindl R (3) The induced electrical current moving in a loop of wire generates its own induced magnetic field. The induced current flows in a direction such that the induced magnetic field has a direction to oppose the original flux change. This is known as Lenz's Law and mathematically it is captured by the negative sign in Faraday's Law (Equation 2) and is illustrated in Figures 1 and 2 below. Induced Magnetic field magnetic induced lines field current lines S Increasing Magnetic Flux / R.H. Figure 1: The permanent magnet illustrated on the left side of the figure is moving towards the coil of electrically conductive wire and so the magnetic flux is increasing. By Faraday's Law of Induction, the increase in magnetic flux in the wire coil results in an induced voltage and current in the coil. The induced current in the wire coil (shown by the right illustration in the figure) moves counter-clockwise so that the induced magnetic field (pointing left) opposes the increase in magnetic flux from the approaching permanent magnet. Note the Second Right Hand Rule (far right illustration) is used to determine the induced current direction.Magnetic field Induced lines magnetic Induced field current lines N Decreasing Magnetic Flux R. M. Figure 2: In this case, the permanent magnet illustrated on the left side of the figure is moving away from the coil of wire and so the magnetic flux is decreasing. By Faraday's Law of Induction, the decrease in magnetic flux in the wire coil also results in an induced voltage and current in the coil. However, the induced current in the wire coil (shown by the right illustration in the figure) now moves counter-clockwise so that the induced magnetic field (pointing right) opposes the decrease in magnetic flux from the retreating permanent magnet. Note again the Second Right Hand Rule (far right illustration) is used to determine the induced current direction. Electromagnetic induction can also occur by replacing the permanent magnet in Figures I and 2 with a current carrying coil of wire that generates its own magnetic field (Figure 3). The current carrying coil (called the "Primary" coil) acts as an electromagnet. The magnetic field of the primary coil can be made to project through an adjacent coil of wire (called the "Secondary" coil). A voltage will be induced in the secondary coil if the magnetic flux from the primary coil changes with time. In this way electrical energy from the primary coil is transferred across free-space to the secondary coil. This phenomenon is called Mutual inductance and is the basis for the transformers that increase and decrease electrical voltage (e.g., the transformer that allows you to charge your cell-phone with 5 volts from a 120V wall plug!) and non-contact electrical charging used more and more in cell-phones, electric tooth brushes, and soon electric cars. Coil 1 Coil 2 UMA B / changing $ induced Galvanometer Figure 3: The magnetic field produced by the current carrying coil (Coil 1, Primary coil) projects through the adjacent coil (Coil 2, Secondary coil). A voltage is induced in the Coil 2 when the magnetic flux from Coil 1 changes.Part A - Magnetic Field Lines and Field Strength: In this part of the experiment we will map the magnetic field around a permanent bar magnet and measure the strength of the magnetic field (B) at two different distances from the bar magnet, and at two different strengths of the bar magnet. . Open PhET Faraday's Electromagnetic Lab Simulation Software. Flash Player is required to run this simulation: > https:/phet.colorado.edu/en.simulation/faraday > Open the first tab at the upper left of the screen, "Bar Magnet" Activate (check box) the options "Show Field", "Show Compass", and "Show Field Meter" (Figure 4). Sample Bar Magnet- Magnetic Field Strength 75 % S Bar Magnet N 50 100 Compass Flip Polanty See Inside Magnet Snow Field Magnetic (B] Field 0.77 G Show Compass Ox 0.65 G By 0.41 G Magnetic show Field Meter 31.81 Field Meter Reset All Figure 4: PhET electromagnetic induction "Bar Magnet" simulation (left illustration) showing the bar magnet, magnetic field lines, compass, and magnetic field meter. The right illustration shows the options activated by checking the boxes. Move the blue Magnetic Field Meter to a corner of the screen. It will be used later. The permanent bar magnet can be positioned in the center of the screen. The bar magnet has a red-colored segment and a "N" on the right side signifying the "North Pole" and a white- colored segment with a "S" on the left end signifying the "South Pole". Note that the compass is also a tiny permanent magnet with a red North Pole and white South Pole. The compass needle will align tangent to the magnetic field lines. Starting with the compass just to the right of the North Pole, slowly drag the compass from the north to the South Pole and sketch the magnetic field lines and the orientation of the compass needle and the north and South Pole of the compass needle (See the sample magnetic field line in Figure 4). Use the sketch box in Part A of the Experimental Data section of this Lab Handout to sketch the magnetic field lines.. Next, move the compass to a corner of the screen. Then drag the magnetic field meter about one centimeter distant from the North Pole along the axis of the bar magnet (just to the right of the magnet) (Figure 5). Adjust the bar magnet strength to 50% and record the value of B read from the magnetic field meter. Then, without moving the magnetic field meter, increase the bar magnet strength to 100% and again record the value of B. 1 Centimeter N Magnetic (B) Field B 18.97 G Bx 18.95 G By 0.75 G 2.26 0 Figure 5: PhET electromagnetic induction "Bar Magnet" simulation showing the position of the magnetic field meter 1 centimeter from the right end of the bar magnet. . Repeat this experiment after moving the position of the magnetic field meter an additional centimeter (total 2 cm) from the North Pole in line with the axis of the bar magnet. Compare the values of B at the position of I em and 2 em for the 100% bar magnet strength. Think hard about this difference! Save a screenshot (screen capture) of the simulation magnetic field for one of your trials and include in the graph section of your lab report. Part B - Induced Voltage/Current: In this part of the activity, we will investigate the magnitude and direction of the induced current in a coil due to changes in the magnetic flux. . Open PhET Faraday's Electromagnetic Lab Simulation Software: https://phet.colorado.edu/en/simulation/faraday Open the second tab at the upper left of the screen, "Pickup Coil". Activate the options "Show Field", "One Loop", and "Show Electrons" (Figure 6). Use the default settings for Loop Area (50%) and change the Magnet Strength to 5096.Pickup dos Indicator Figure 6: PhET electromagnetic induction "Pickup Coil" (Left illustration), showing the permanent bar magnet, coil of wire and light bulb, and magnetic field, and the settings tables Right illustration). Referencing the equations for Magnetic Flux (Equation 1) and Faraday's Law of Induction (Equation 2), change the variable settings as described below (i.e., Coil Area and Magnetic Field Strength (Equation 1) and Number of Coils (Equation 2)) and then move the North Pole of the bar magnet through the coil slowly and then quickly and observe the relative "brightness" of the light-bulb between the "fast" and "slow" magnet movement and between the changes in the variables. The "brightness" increases as the length of the "light rays" emanating from the light-bulb increase. Record your observations in the Part B Data Table section. Return the values to the starting settings after each change in variables: o Increase the coil area from 50% to 100%. Increase the Magnetic Field Strength from 50% to 100%. o Increase the Number of Coils from 1 to 3. Record also what happens if you place the North Pole of the Bar Magnet inside the coil and do not move it. Think about what combination of "design" variables would produce the greatest induced voltage! . Continue the experiment by setting the coil area and magnetic field strength to 100%, the number of coils to 3, and replace the lightbulb with the "Volt Meter" (Figure 7). In this case, move the bar magnet's North Pole slowly towards the coil and observe how the needle on the voltmeter moves (left or right). Observe if there is a difference in the needle direction when you move the bar magnet North Pole towards or away from the coil. Repeat this experiment using the bar magnet's South Pole. Save a screenshot (screen capture) of the simulation induced voltage current for one of your trials and include in the graph section of your lab report.S Figure 7: PhET electromagnetic induction "Pickup Coil" showing the permanent bar magnet, coil of wire and Volt Meter. Part C - Mutual Induction: In this part of the experiment we will investigate how the principle of mutual induction allows an electrically powered "Primary" wire coil to transfer electrical energy to a "Secondary" wire coil across free space. A current carrying coil produces a magnetic field and can replace the permanent magnet in Part B. . Open PhET Faraday's Electromagnetic Lab Simulation Software: > https://phet.colorado.edu/en/simulation/faraday Open the fourth tab at the upper left of the screen, "Transformer" > Activate (check box) the options "Show Field", "Show Electrons". Set the Primary coil to "4 Loops" and the Secondary Coil to 3 Loops (Figure 8) Electromagnet- ripary Cull [Powered by PUTUP COL- Figure 8: PhET electromagnetic induction "Primary Coil" powered by a DC Battery (Left illustration), the Secondary Coil with a light bulb, and the settings tables (Right illustration).Noting that the DC (Direct Current) battery provides a constant source of electrical power to the Primary Coil, and referencing Equations I and 2. observe and record the change (if any) of the magnetic field produced by the Primary Coil and the relative "brightness" of the light-bulb attached to the Secondary Coil when the Primary Coil is stationary. (Record your Observations in the Part C Data Table). Observe and record the change (if any) of the magnetic field produced by the Primary Coil and the relative "brightness" of the light-bulb attached to the Secondary Coil when the Primary Coil is moved slowly and then quickly through the Secondary Coil. (Record your Observations in the Part C Data Table). Now change the setting of the Primary Coil from DC to AC (Alternating Current set at 100% ) and activate the "Volt Meter" instead of the light bulb (Figure 9) Electromagnet Voll Meter Current Source AC Current Supply Show Field Show Compass show Field Were Show Elenao's -Pickup Coll COL AL Foocroc Priman, Col Show Fledions Figure 9: PhET electromagnetic induction "Primary Coil" powered by an AC power source (Left illustration), the Secondary Coil with a Volt Meter, and the settings tables (Right illustration) Position the Primary coil as shown in Figure 9. Noting that the AC (Alternating Current) provides a continuously varying supply of electrical power to the Primary Coil, and referencing Equations I and 2, observe and record the change (if any) of the magnetic field produced by the Primary Coil and the movement of the Voltmeter Needle attached to the Secondary Coil when the Primary Coil is stationary. (Record your Observations in the Part C Data Table). . Now move the Primary Coil into the center of the Secondary Coil. Observe and record the change (if any) of the magnetic field produced by the Primary Coil and the movement of the Voltmeter Needle attached to the Secondary Coil when the Primary Coil is stationary. (Record your Observations in the Part C Data Table). Save a screenshot (screen capture) of the simulation mutual inductance for one of your trials and include in the graph section of your lab report.Part D - Electrical Power Generation: . In this part of the experiment we will investigate how the principle of mutual induction allows electrical power to be generated by rotating a magnet near a coil of electrically conducting wire. Note again that this is of great technological importance as this is the way that hydroelectric, coal, oil, gas, nuclear, wind, and tidal Power Plants generate electricity for our modern civilization. . Open PhET Faraday's Electromagnetic Lab Simulation Software: https:/phet.colorado.edu/en/simulation/faraday > Open the fifth tab at the upper left of the screen. "Generator" > Activate (check box) the options "Show Field", "Show Compass". Set the Primary coil to "2 Loops", the Bar Magnet strength to 50% and the "Loop Area" to 50% (Figure 10). lar Magnet- Frangh volt Meter External Power Supply Compass I grow Field Show Flaid Meter Pickup Coll Wire CALL Figure 10: PhET electromagnetic induction "Generator" powered by an external power source (Water - as "Hydroelectric Power" using water behind a dam) that turns a water-wheel with a magnet attached (a "Turbine"), and that causes a continuously changing magnetic field inside the adjacent wire coil. Vary the following "design" variables and record your observations of the magnetic field, voltage produced, and the movement of the voltmeter needle in the Part D Data Table: o Bar Magnet Strength from 50% to 100% Coil (Loop) Area from 50% to 100% Increase the external power supply water-flow-rate to increase the "Turbine" revolutions per minute (RPM) from 10RPM to 50RPM. Watch the change in the magnetic field carefully at the lower 10RPM setting. Think what settings of the variables will produce the greatest electrical power output. Save a screenshot (screen capture) of the simulation power generation for one of your trials and include in the graph section of your lab report.Analysis: . Part A - Magnetic Field Lines and Field Strength: 1. Magnetic Field Lines: As you sketch the magnetic field lines, include which part of the compass needle points towards the North Pole of the bar magnet. The North or South Pole of the Compass needle? Include this in your Lab Report. 2. Magnetic Field Strength; How much does the value of B increase on the magnetic field meter when the magnetic field strength of the bar magnet is doubled at I cm from the North Pole of the magnet? Does this make sense? Why? Explain in your Lab Report. 3. Magnetic Field Strength: Did the value of B increase or decrease when the magnetic field meter was moved I em to 2 cm (double the distance) at 100% bar magnet strength? Did the value of B double, fall in half, or something else? (Hint - Think of how the electrostatic Coulomb Force changes with distance!) Explain in your Lab Report. . Part B - Induced Voltage/Current (Reference Equations ] and 2 in your responses!): 1. How does the speed at which the bar magnet is moved effect the "brightness" of the light bulb? Explain in your lab report. 2. How does the coil area effect the "brightness" of the light bulb? Explain in your lab report. 3. Why does magnetic field strength effect the "brightness" of the light bulb? Explain in your lab report. 4. Why does the number of coils effect the "brightness" of the light bulb? Explain in your lab report. 5. What happens to the lightbulb "brightness" when the bar magnet is placed inside the coil of wire and not moved? Explain in your lab report. 6. What happens to the lightbulb "brightness" if you move the coil over the bar magnet instead of the bar magnet through the coil? Explain in your lab report. 7. What direction does the voltmeter needle move when the North Pole is pushed into or withdrawn from the wire coil? The South Pole? Explain in your lab report. 8. What settings of the electromagnetic induction "design" variables (Equations I and 2) give the greatest voltage? Explain in your lab report.. Part C - Mutual Induction: 1. How does the "brightness" of the light-bulb change when the DC powered Primary coil is stationary? Explain in your lab report. 2. How does the "brightness" of the light-bulb change when the DC powered Primary coil is moved slowly and then quickly towards the secondary coil. Explain in your lab report. 3. How does the voltmeter needle respond when the AC powered Primary coil is near the secondary coil? When placed inside the secondary coil? Explain in your lab report, . Part D - Electrical Power Generation: 1. How does the voltmeter respond when the bar magnet strength is increased from 50% to 100% at 10RPM? Explain in your lab report. 2. How does the voltmeter respond when the loop area is increased from 50% to 100% at 10RPM? Explain in your lab report. 3. How does the voltmeter respond when the water flow rate is increased to cause the "turbine" to rotate fast from 10RPM to 50RPM? Explain in your lab report. Lab Report: When writing the lab report, you must review and follow very carefully the Physics Lab Report instructions handout. In your lab report, include the Cover Page, Objectives, Theory, Equipment, Data, Graphs, Calculations, Conclusions, Sources of Error, and References. Remember to show all equations and calculations in detail and to round the results to the correct number significant digits and precision. In the conclusions section, be sure to summarize the final results, comment on the agreement or disagreement of the results with the theory or expectations, and discuss what you personally learned from this experiment and your observations/comments. Submit your complete lab report electronically by the due date!Physics . Online Lab: Electromagnetle Induction Tables of Data and Results . Part A - Magnetic Field Lines and Field Strength: Sketch the magnetic field around a bar magnet - show the magnetic field and the North/South Pole directions. Magnetic Field Strength at 1 cm and 2 cm (50% and 100% Bar Magnet Strength) Location of Magnetic Field Meter 50% Bar Magnet 100% Bar Magnet from North Pole of Bar Magnet Strength Strength 1 cm 2 cm. Part B - Induced Voltage/Current: Record your observations of the relative "brightness" of the lightbulb as a function of the change in the electromagnetic induction 'Design" variables in Equations I and 2: Light Bulb "Brightness" verses the Electromagnetic "Design" variables (Equations 1 and 2) Variable Change Slow Magnet Motion Fast Magnet Motion Coil Area 50% Coil Area 100% Magnetic Field Strength 50% Magnetic Field Strength 100% Number of Coils = 1 Number of Coils = 3 Record your observations of the voltmeter needle response to the bar magnet North and South Pole movement towards and away from the coil: Voltmeter Needle Response to the North and South Pole Magnet moving towards or away from the Coil Magnet Pole and Movement Voltmeter Needle Response North Pole Towards Coil North Pole Away from Coil South Pole Towards Coil South Pole Away from CoilPart C- Mutual Inductions Record your observations of the relative "Brightness" of the lightbulb when the DC powered Primary Coil is stationary or moved slowly quickly through the Secondary coil: Secondary Coil relative Brightness vs DC Powered Primary Coil Movement Primary Coil Movement Light Bulb "Brightness" No Movement Slow Movement Quick Movement Record your observations of the AC Powered Primary coil's effect on the Secondary Coil Voltmeter response: Secondary Coil Voltmeter Response vs AC Powered Primary Call Location Location of AC Powered Primary Coil relative to the Secondary Coil Voltmeter Response Magnetic Field Change Primary coll is to the left of the Secondary Coil Primary Coil is inside the Secondary Call. Part D - Electrical Power Generation: Record your observations of the voltage produced and motion of the voltmeter needle as a function of the bar magnet strength, coil area, and "Turbine" rotation rate: Electrical Power Generation Vs. Bar Magnet Strength, Coil Area, and Turbine RPM Location of AC Powered Primary Coll Voltmeter Maximum relative to the Secondary Coil Voltmeter Direction Value Bar magnet strength 50% Bar magnet strength 100% Coil Area 50% Coil Area 100% Turbine 10 RPM Turbine SORPM