Lab 8_FaradaysLaws_updated

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Dec 6, 2023

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PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb Lab 08: Magnetic Field and Faraday’s Law You will need to run a simulation to do the lab. Answer the following questions as you work through the lab. Write your answers in blue . (Note that we may miss your response if it does not stand out) Re-load the file in Word or PDF format in Canvas before the due date. Objective In this lab, you will (i) Investigate the properties of magnet and (ii) Use Faraday’s Law to predict the properties of induced emf in a coil. You will investigate the induced emf generated by a moving bar magnet and coil. You will: ● Move a bar magnet near one or two coils to make a light bulb light-up. ● View the magnetic-field lines. ● Use an Ammeter (current meter) to show the direction and magnitude of the induced current. ● View the magnetic field-lines. ● Observe how the compass needle deflection and the electron movement inside the coil change by changing the source of an electromagnet from DC to AC. Theory: In the previous lab, we did an experiment to show how the current flowing through a wire produces a magnetic field around it. In this lab, we will study how the changing magnetic fields produce electric fields, a phenomenon known as ‘ Magnetic Induction ’. Faraday’s Law:

PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb According to Faraday's Law of Induction, a changing magnetic flux, Ф , through a coil induces an EMF ( electromotive force -- a voltage ) given by: ε =− N ΔΦ Δt ………. (1) where Φ = ⃗ B. ⃗ A is the magnetic flux due to a magnetic field ( ⃗ B ) passing through the cross-sectional area (A) of the loop of a wire, ⃗ A is a vector perpendicular to the area of the loop. N is the number of turns (loops) of the wire in the coil. For this experiment, the area of the coil remains constant and as the coil passes into or out of the magnetic field, hence Eq. 1 can be re-written as; ε =− NA ΔB Δt … ……. (2) Lenz's law states that the current induced in a circuit (loop) due to a change in a magnetic field is directed to oppose the change in flux and to exert a mechanical force which opposes the motion. Simulation: Open Faraday’s Electromagnetic Lab https://phet.colorado.edu/sims/cheerpj/faraday/latest/faraday.html? simulation=faraday Please take a few minutes to become familiar with different tabs and select options present in the simulation. 1. Bar Magnet 1. Click on the ‘Bar Magnet’ Tab you should see a bar magnet and a compass on the screen. You should note that the color red refers to North- and white refers to South-poles of the magnetic. Place the compass at the North end of the bar magnet and observe which way the “red tip” of the compass points. Move the compass to the South end, and observe where the “red tip” of the compass points. Based on your observation, describe how the compass works: [2 Points] The compass works by the red tip always pointing to

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PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb the south pole on the magnet. When moving the compass near the north pole on the magnet, the gray tip is attracted. All in all, a compass works by the “north” direction, or red tip always pointing to the magnetic south pole, even though we declared it the north pole since the compass points north. The compass works by the red tip always pointing to the south pole on the magnet. When moving the compass near the north pole on the magnet, the gray tip is attracted. All in all, a compass works by the “north” direction, or red tip always pointing to the magnetic south pole, even though we declared it the north pole since the compass points north.

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PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb 2. Use your response above to explain why the geographic North-pole is the magnetic South-pole. [2 Points] The north pole is the geographic south pole because the north pointing tip on the compass is attracted towards the north pole. The North pole is magnetically the south pole because it attracts the north tip on a compass and does not repel that tip

PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb 3 . Check the “ show field ” box if it is not already checked. This shows how the compass needle would orient itself at each point around the bar magnet. Joining these in the direction of the red arrow gives essentially the field line diagram of the bar magnet. Sketch a diagram of these using PowerPoint/Paint (some drawing tool) and paste your sketch below. Use arrows to represent the direction in which the red tip (N-pole) points. Make sure you label the poles of the magnets properly. [You need this diagram for (5). Do not delete it yet!] [5 Points] 4. Place the compass next to the North-Pole of the bar magnet and press the Flip Polarity button. What happens to the magnet and the compass? [2 Point] The poles on the magnet switch so that the north pole on the magnet became the south pole. The effect on the compass is that it went from the red tip pointing away from the magnet to pointing towards it since it is now next to the south pole of the magnet. 5. Click ‘See Inside Magnet’. What do you see? [3 Points] When the see inside magnet box is clicked, it shows straight lines going from the south to the north poles. This shows that the compass will point towards the south pole of the magnet and the lines carry that strength throughout the magnet, also showing the repelling nature from the north pole 6. Click ‘Show Field Meter’ and move the meter around outside the magnet and answer the following questions: [6 Points] Where is/are magnitude of B maximum? What is/are the value/s there? _____ maximum: ___ 78.3. From the upper left corner of the north pole of the magnet the value can read as 78.3 as well.

PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb ______ Where is/are magnitude of Bx maximum? What is/are the value/s there? _ The maximum value of Bx is 11.63, located near the north pole of the magnet. This value is below the north pole, offset from the middle of the pole to the left. This value was also taken by keeping the cross hair within the field meter from touching the magnet at all ____________ Where is/are magnitude of By maximum? What is/are the value/s there? ___ The maximum value of By is 75.62, located at the lower right corner of the south pole. This value was also taken by keeping the cross hair within the field meter from touching the magnet at all. _________ Magnetic Field Vector : Sketch the bar magnet using PowerPoint/Paint (or some drawing tool) and show the regions where [4 Points] a) B x is positive and negative [Note the angle specified in the B-Field meter]. b) B y is positive and negative Place the B-Field meter at a location to the left and underneath the bar magnet . Take a screenshot and paste below. What are the Bx, By and ⃗ B values ? Verify the mathematical relationship between the three. Also note the value of angle Θ . What is the mathematical relationship between B x and B y and angle Θ? Verify this for the values noted. Show your calculation in order to get full credit. [4 Points]

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PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb  B= 6.99, Bx=3.18, By=-6.22, θ=-62.88  B=√Bx2+By2 = √3.182+-6.222 = √48.8008 =  6.985756938 →6.99  θ= tan-1(by/bx) = tan-1( -6.22/ 3.18)  = tan-1(-6.22/3.18) = tan-1(1.955974843)  = -62.9

PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb 2: Electromagnet – Is Electromagnetism Reversible? 1. Choose the Electromagnet Tab . You should see a battery attached to a loop of coil (an electromagnet) and a compass on the screen. Make sure the current source is set to DC and uncheck the “show field” box. Set the number of loops to 4. Move the compass around the electromagnet and describe what it does: [2 Points] The compass’s red tip points towards the tail of the battery and the gray tip points towards the head of the battery when the compass is above the center of the battery. When moving the compass towards the tail of the battery, the red tip slowly moves to point downwards and the opposite when moving the compass towards the head of the battery. The gray tip of the compass always points towards the coils whenever it is being moved around them 2. Move the compass around the electromagnet in order to determine the North and South poles. Draw a picture of the electromagnet coil and label the ends as either North or South Pole. (No need to make it complicated, just label them properly). On your diagram indicate the direction of current flow in the coil (Note: the simulation shows the flow of electrons. How does this flow relate to the direction of conventional current?) [3 Points] 3. Now check the “ show field ” box and observe the magnetic field lines. How does the magnetic field of the electromagnet compare to that of the bar magnet? Add the field lines to your diagram above. [2 Points] The magnetic field of the electromagnet is centered around the coils. The field lines also have 2 major segments. One on top and one on bottom split by the center of the coils. The bar magnet’s fields are split like this to some extent but it is only split straight within the magnet whereas the coils split like that beyond just the coils. As soon as the field is through the magnet it curves again above and below but does not necessarily curve as steeply as the coils do. The curves of the field lines around the electromagnet are more pronounced and curved more drastically than the bar magnet 5. Change your current source from DC to AC and describe what the compass does? [2 Points] The compass continually switches as the electron directions shift. The magnetic field is consistently being shifted and the compass reflects this by the poles constantly flipping sides to keep up with the changing magnetic field

PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb 6. Observe the electrons in the AC current source and compare their movement to those in the DC current source. Explain the difference between DC and AC in terms of electron movement. [2 Points] In the DC current source, the electrons move in a single direction. However, in the AC current source, the direction of the electrons change periodically. 7. Change back to DC source. Use the field-meter to observe the field at various spots. Where is the B strongest and where is it weakest? [2 Points] The strongest value of B can be achieved on the coils and to the immediate left and right if keeping the cross hairs of the field meter off the coils. The weakest values of B can be found above the battery. The further above the battery the meter is, the weaker the B value becomes 8. Place the field meter near one of the ends of the coil (set the number of loops to 1). Write down the value of B . Start increasing the number of loops and record corresponding value of B . [2 Points] No. of Loops BValue ( G 1 75 2 150 3 225 4 300 Perform a linear fit of this data using Excel and paste the graph below. Make sure the equation of linear fit is displayed. [5 Points]

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PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb [Helpful Video: https://www.youtube.com/watch?v=L_a8Z0BVjyM ] Based on the graph explain whether linear fit is an appropriate choice to describe the relationship between B and Number of Turns of the coil? [1 Point] Yes a linear fit is an appropriate choice to describe the relationship between B and the turns of the coil. According to my graph and data, the relationship is direct. There line fits the data perfectly as each loop increases the B value by 75G. There also is no intercept so at 0 loops there will be a B value of 0, which is expected. As per my data and graph, there would be no better fit to the graph than a linear fit.

PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb 3: Pickup Coil 1. Choose the ‘ Pickup Coil ’ tab. Set the number of loops to “1” and loop area 50%. Write your observations of the light bulb when [4 Points] a) the magnet is not moving and is not inside the loop. The light bulb is off b) the magnet is moving and is not inside the loop. The light bulb is off and flickers on occasion but overall remains off c) the magnet is not moving and is inside the loop. The light bulb is off d) the magnet is moving and is inside the loop. The light bulb flickers are varying light intensities while the magnet is moving 2. If you change the speed of the magnet, does it affect your results? If so, how? [2 Points] The slower the magnet is moved, the smaller the light intensity. If the magnet is moved faster, then the intensity will be greater. 3. If you change the strength of the magnet, does it affect your results? If so, how? [3 Pts.] Increasing the strength of the magnet increased the intensity from the light bulb when it lights up. Decreasing the strength of the magnet will decrease the intensity of the light bulb when it comes on. 4. Increase the number of loops to “3” and note how it affects your results. [2 Points] Increasing the number of loops increases the intensity from the bulb when it lights up 5. Increase the loop area to “100” and note how it affects your results. [2 Points] Increasing the loop area increases the intensity of the light bulb when it is on. The intensity still increases the faster the magnet is moved. 6. Replace the bulb with the voltage indicator . Observe what happens to the voltage induced as you change [4 Points]

PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb a. the speed of the magnet: __ There is more voltage change the faster the magnet is moved when compared to no movement and slow movement of the magnet. _______ b. the strength of the magnet: _ There is more voltage change the stronger the magnet is. When decreasing the strength of the magnet, the change in voltage will also decrease. _________ c. number of loops to 3: ______ The change in voltage increases when the number of loops increase to 3 from 1 loop. d. increases the loop area to 100: ___________ When there is only one loop with an area of 100%, the voltage will slightly change when the magnet is slowly moved and increases when the magnet is moved quickly. There is slightly more change in voltage when the area is bigger than when it is smaller with a single loop. 7. What is the sign of the induced voltage as the North -pole end of the magnet moves towards the coil. [1 Point] Sign __ negative ______ 16. As the magnet passes through the coil and the South-pole end recedes away from the coil, what is the sign of the induced voltage? [1 Point] The sign is positive. 17. Relate these two findings to Lenz’s law. [3 Points] Lenz’s law states that the current induced in a circuit from a change in magnetic field is opposite the change in flux and exerts a force opposite to the motion. The two prior responses are related to one another via this property. When the north pole of the magnet approaches the coil, the flux increases and the law states the change in magnetic field is opposite the flux, thus showing a negative sign. When the south pole side recedes from the coil, the flux will decrease which by the law shows the sign will be positive. 4: Transformer 1. Why doesn’t the transformer work with DC voltage? (Hint: Faraday’s law). [2 Points]

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PHYS 2 Lab Fall 2023 Summer Lab PHYS 2 LAb Faraday’s law states that a changing magnetic flux through a coil induced EMF. In this case when losing a DC voltage, the current is constant. As a result of this constant current, the magnetic field is not changing this no EMF is produced to affect the transformer 2. Switch the current source to AC. What five things can you adjust to get the highest maximum voltage? [3 Points] Things that can be adjusted to get the highest maximum voltage is operating at high frequencies, shell form design, increasing the transformer’s capacity, laminating the core, and reducing the magnetizing effect to reduce the loss dle to hysteresis 5: Generator 1. What does RPM (written in the wheel) stand for? [1 Point] RPM stands for revolltons per minute 2. Open the Tap. What four things can you adjust to get the highest maximum voltage? [2 Points] Things that can be adjusted to achieve the highest maximum voltage includes increasing the area of the coil, increasing the number of coils, increasing the RPM, and increasing the strength of the magnetic field. 3. In previous labs the magnet was moved in-out (or towards/away) from the coil for the bulb to glow. However, in this case the magnet is rotating but the bulb is still glowing. Explain how is this possible. (Hint: Think about Flux! Faraday’s law). [3 Points] Faraday’s law states a changing magnetic flux through a coil induces EMF. The moving magnet is creating a change in the magnetic field, and as the magnetic field is changed, the flux will also change which in turn will create EMF. This created EMF will continue as long as the magnet is rotating so the bulb will remain lit.

Lab 8_FaradaysLaws_updated

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