Ch22_ListroR

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Ch. 22: Induced Current

= Guiding Questions = == = ** Virtual Lab ** = Due Date: December 7, 2011

__**Objective:**__ To detect an induced current using a voltage meter.

__**Hypothesis:**__ A magnetic field is required to induce a current in a loop of wire. Strength of magnetic field, area, and angle influence the direction and magnitude of induced current. This is solely based on my previous knowledge of the magnetic flux equation, flux=BAcos(angle)

__**Procedure:**__ **1. Induction With a Permanent Magnet**: Click on tab called //Pickup Coil//. **2. Induction With an Electromagnet:** Click on tab called //Transformer//.
 * In the middle of the right side of the screen click on voltage meter to switch the indicator on the coils from a light bulb to a voltage meter. Also click on the button that displays all charges.
 * Click and drag the coil over the north pole of the magnet. Observe the voltage meter and the green dots that represent electrons in the coil.
 * Repeat moving the coil more slowly. Observe the voltage meter. Record your observations in your Observation Table.
 * Repeat Steps b and c, moving the coil over the south pole of the magnet. Observe the voltage meter.
 * Now click on the magnet. Quickly move the north pole of the magnet in and out of the coil. Repeat slowly. Move the magnet to the other side of the coil and repeat this step using the south pole. Observe the meter.
 * In the middle of the right side of the screen click on voltage meter to switch the indicator on the coils from a light bulb to a voltage meter. Also click on the button that displays all charges.
 * Move the smaller coil inside the larger coil. Observe the voltmeter and the green dots that represent electrons in the larger coil. Record your observations in your Observation Table.
 * Decrease the current in the smaller coil, by moving the slider on the battery to the left until it reads 5 V. Repeat Step b.
 * Reverse the current in the smaller coil, by moving the slider on the battery all the way to the left. Repeat Step b.
 * Replace the DC battery with AC power supply, by clicking on the AC button in the box labeled Current Source on the top right side of the screen. Repeat Step b.
 * Increase the magnitude of the power supply by moving the slider on the left side of the power supply up. Repeat Step b.

__**Data:**__ Permanent Magnet Electromagnet
 * **Experiment** || **Observation** ||
 * Drag coil over north end of magnet || Voltage meter deflects to the left (negative direction) then goes back to its original position; dots in coil turn counterclockwise ||
 * Drag coil slowly over north end || Less deflection compared to when the coil is moved over pole quickly ||
 * Drag coil over south end || Voltage meter deflects to the left (negative direction) then goes back to its original position; dots in coil turn counterclockwise ||
 * Coil over south end, slowly || Less deflection compared to when the coil is moved over pole quickly ||
 * Drag north/ south end of magnet into coil || The voltage meter moves to negative and positive when magnet moves in and out. Dots move counterclockwise and clockwise when magnet moves in and out. ||
 * **Experiment** || **Observation** ||
 * Smaller coil moved inside larger one || When it enters, the dots move counterclockwise, and the voltage meter deflects to the negative direction and then moves back to its original position. ||
 * Decrease voltage to 5 V || Voltmeter deflects half as much and the dots move half as much. ||
 * Reverse current in small coil || Voltmeter deflects in the positive direction, and the dots move clockwise. ||
 * Replace DC power with AC power || Voltmeter and the dots move back and forth, as does the AC power. ||
 * Increased magnitude of AC power || Voltmeter and dots move back and forth faster. ||

__**Discussion Questions:**__ > Yes, the galvanometer would deflect at a greater angle when the magnet or coil moved at a faster velocity as compared to when they moved at a slower rate.
 * Based on your observations from the first part of the lab, did the speed of the motion have any effect on the galvanometer?

> It did not have any effect. The galvanometer and the dots would both move in the same direction.
 * In the first part of the lab, did it make any difference whether the coil or the magnet moved?

> The voltmeter shows that there is current present in the wire.
 * Explain what the voltage meter readings revealed to you about the magnet and the wire coil.

> <span style="color: #000034; font-family: Arial,Helvetica,sans-serif;">The magnet or circuit must be moving, which must cause a change in flux, and therefore induce a current.
 * <span style="color: #000034; font-family: Arial,Helvetica,sans-serif; font-size: 10pt;">Based on your observations, what conditions are required to induce a current in a circuit?

> Angle, area, and magnetic field are all factors that influence these.
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 10pt;">Based on your observations, what factors influence the direction and magnitude of the induced current?

__**Conclusion:**__ My hypothesis was correct. This lab showed that changing the magnetic flux can induce current. In order to do this, one must either alter the magnetic field strength, area, or angle. This was able to be performed in the lab by moving the magnet or by moving the circuit through the magnet. This movement strengthened or weakened the magnetic field strength depending on the direction the magnet was moved to or from the circuit. In turn, this altered the magnetic flux. Because this was a virtual lab in an assumed perfect environment, we can assume there was no error in this lab.