Physics 2 Lab 8

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Jan 9, 2024

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Lab 8- Electromagnetic Induction Purpose: To analyze the factors that affect induced voltage and setup a transformer and see how they work. Apparatus: PASCO interface with Capstone, DC power supply, AC power supply, PASCO voltage sensor, coil kit(with iron filings,iron cores and permanent magnets), two multimeters with banana leads. Procedure: Part I- Shape of the magnetic field around a permanent magnet and a solenoid coil electromagnet ● Switch the current and voltage down on the DC power supply and connect the DC power supply to the 1600-turn solenoid coil. ● Turn the current to 0.5A carefully. Place the coil on its side so it is in the horizontal direction. Lay a piece of cardboard flat on top of the coil so the coil is under the middle of the cardboard. ● Shake little bits of filings over the cardboard then tap the end of the cardboard for the filings to settle. ● After visualizing the field line coils, turn the power supply off. Pour the filings back to the shaker.

● Place the permanent magnet under the cardboard and sprinkle more filings as necessary to see the magnetic field of the permanent magnet. Pour the filings back into the container. Part II- Using magnetic flux to induce EMF in a coil ● Switch on the interface and connect the voltage sensor. Attach the red and black connectors from the voltage sensor to the 200 turn coil. ● Right click on the input for the voltage sensor in the Hardware setup menu in capstone. Set the sampling rate to 200Hz. Create a graph of the voltage sensor as a function of time by dragging the graph from the right hand Displays menu. ● Set up a graph of the voltage as a function of time by dragging the graph from the right hand Displays menu. Select the select measurement button next to each axis to set the parameters to voltage and time. ● Make sure that the magnet does not strike the floor. Hold the magnet about 2cm from the coil. Press record and drop the magnet through the coil and stop recording. Two peaks will appear. ● Use the cursor tool in the top menu bar to find both peaks values. ● Repeat the data analysis and collection procedure again with two magnets tapped side by side such that poles together. ● Repeat the steps for the 400 and 800 turn coils to investigate how EMF varies with the number of loops in a circuit. Part III- Transformer

● Place two 400 turn coils side by side as in the figure below and connect one as your primary to an AC power supply. Connect multimeters to both coils and set them to measure AC voltage. ● Switch on the power supply and adjust it to 6V AC setting. Record the primary and secondary voltages indicated by the multimeters. ● Turn off the power supply and place the coils on the U-shaped iron core and place a straight iron core across the top to complete the square core arrangement. Turn on the supply and set it to 6V AC and again record the voltages. ● Turn off the power supply and switch the secondary coil out for the 200 turn coil. Connect a multimeter to the primary coil as well as the secondary coil. Set up both meters to AC voltage. ● Switch on the power supply and set it to 6V AC and measure and record the primary and secondary voltages. ● Repeat the steps with a 400 turn primary and secondary and repeat again with 400 turn and 800 secondary. Precautions: ● Make sure to tap the edge of the cardboard to allow the filings to settle. ● Ensure that the magnet does not strike the floor so it does not break. ● Be sure to turn the power supply all the way down on the DC power supply before connecting it to the 1600 turn coil. Errors:

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● Do not turn on the current higher than 0.5A, otherwise the coil may burn. ● Turn the power supply off before returning the filings back to the shaker. ● The magnet falling causing it to break. Data & Table: Part 2: # turns Incoming peak Outgoing peak 400 0.033V -0.053V 800 -0.069V 0.112V Part 3: Configurations primary voltage V 1 (V) secondary voltage V 2 (V) Air core 5.8V 0.08V Complete square core 6.14V 5.30V N 1 : N 2 = 400/200 N 1 : N 2 = 400/400 N 1 : N 2 = 400/800 V 1 (V) V 2 (V) V 1 (V) V 2 (V) V 1 (V) V 2 (V)

6.14v 2.58V 5.8V 0.08V 6.14V 10.56V

Conclusion: In part I of this experiment, we were able to determine the shape of a magnetic field around a permanent magnet by pouring iron filings on a cardboard and putting a magnet underneath the cardboard. We saw that the magnetic field was out towards us no matter the direction we moved

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the magnet underneath the cardboard. In part II of the experiment, we used a magnetic flux to induce EMF in a coil. We used Faraday’s Law to see the relationship between turn coils and induced EMF and the role magnetic field plays in it. In part II, we saw that as we dropped a single magnet through a 200V, 400V and 800V turn coil, there was an increase in the induced EMF which supports Faraday’s Law that the induced voltage is proportional to the rate of the change of the magnetic flux through the coil. According to our graph of the 200 turn coil-1 magnet, the incoming peak was 0.007V while the outgoing peak was -0.053v. In our graph of the 200 turn coil-2 magnets, 0.021V while the outgoing peak -0.012V. This was consistent through our 400 coil and 800 turn coils too. In part III, we saw that the induced EMF increased as we added a straight iron core to the apparatus. The induced EMF stayed the same for the primary multimeter since it was directly connected to the power supply compared to the secondary multimeter whereby its EMF increased as we increased the number of turn coils. The primary remained 6.14V whereby the secondary increased from 2.58V in the 200 turn coil to 10.56V in the 800 turn coil. Questions: Question 1. The shape of the magnetic field should be the same for both types of magnets. Did both of your magnets create roughly the same shape field? Yes, both types of magnets created the same shape. Question 2. Faraday’s law states that induced voltage is proportional to the rate of change of the magnetic flux through the coil. In light of this, why is the outgoing peak higher than the incoming peak?

Faraday’s Law states that the induced voltage is proportional to the rate of change of the magnetic flux through the coil. The outgoing peak was higher than the incoming peak because the magnet moved faster as it dropped through the coil. Question 3. Why are the peaks opposite in direction? Use Faraday’s law to support your answer. The peaks are in opposite direction because the change in magnetic field at one end of the coil is opposite from the other, this proves Faraday’s law that the voltage induced is dependent on the circumstances of the change in magnetic field. Question 4. How is the emf affected by passing a larger magnetic field through the coil? Again, use Faraday’s law to support your answer. The EMF is proportional to the change in magnetic flux so the EMF will increase since the magnetic field is larger. Question 5. How is the emf affected by the number of turns of the coil? Does this agree with Faraday’s law? The EMF is directly proportional to the number of turns of the coil so according to Faraday’s Law as the number of turns of the coil increases as the induced EMF increases. Question 6. What effect did the iron have on the voltage induced on the secondary? It is often stated that the iron in the cores focuses the magnetic field lines because they prefer to travel through the iron rather than the air. How then does Faraday’s Law (and the flux through the secondary) explain the effect iron has on the voltage induced on the secondary?

The iron increased the voltage from 0.08V to 5.30V. Faraday explains this effect by stating that when the magnetic flux connecting a circuit changes, there is an EMF induced in the circuit proportional to the rate of change of the flux connection. Hence why our voltage increased from 0.08V to 5.30V. Question 7. What kind of out to input relationship did you see in your results? For example, when your secondary had twice as many turns, did the transformer produce a stepped-up voltage on the secondary? How much was the voltage increased? Do a similar comparison of output to input voltage for the other two cases as well. We saw that as the number of coils increased, so did the EMF, hence a direct relationship with the out to input relationship. The primary had the same voltage since it was connected directly to the power supply whereas the voltage for the secondary transformer increased from 0V to 10.56V in the 800 coil. The voltage doubled from its value of 5.8V in the 400 coil to 10.56 in the secondary showing a stepped-up voltage.

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