Ch22

= = toc

=Guiding Questions 1-17=

== =Virtual Lab=

** Virtual Laboratory: Electromagnetic Induction **

When an electromagnet is placed near a loop of wire, it induces a current.
 * Objectives: **
 * 1) Detect an induced current using a voltage meter.
 * 2) Summarize the relationship between the magnetic field of a magnet and the current induced in a conductor.
 * 3) Evaluate what factors affect the direction and magnitude of an induced current.

What conditions are required to induce a current in a loop of wire? What factors influence the direction and magnitude of the induced current?
 * Hypothesis **
 * A magnetic field is required to induce a current in a loop of wire, and there must be motion.
 * Magnitude is influenced by the velocity, magnetic field strength, area, and the angle between the area and magnetic field. Direction is influenced by the way magnetic field and current are aligned.

Rationale - My hypothesis is based off the equation for magnetic flux Flux = BAcos(phi)


 * Procedure: **
 * 1)  You can find the virtual lab at __ [] __.


 * 1) On the left side of the screen scroll down and click on the Electricity, Magnets & Circuits link. Click on the virtual lab called “Faraday’s Electromagnetic Lab.” It should automatically download and open on your computer.


 * 1) Prepare an observation table. You need two wide columns, labeled //Experiment// and //Observation//. For each part of the lab you will write a brief description of what you do in each step under //Experiment//. In the //Observation// column, record your observations.


 * 1) ** Induction With a Permanent Magnet ** : Click on tab called //Pickup Coil//.
 * 2) 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.


 * 1) 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.


 * 1) Repeat moving the coil more slowly. Observe the voltage meter. Record your observations in your Observation Table.


 * 1) Repeat Steps b and c, moving the coil over the south pole of the magnet. Observe the voltage meter.


 * 1) 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.


 * Observation-Part I**
 * Experiments || Observations ||
 * Click and drag the coil over the north pole of the magnet || Dial deflects in the negative direction. The electrons move downward. ||
 * Repeat moving the coil more slowly || Same thing as above, but the dial just deflects less. ||
 * Repeat Steps b and c, moving the coil over the south pole of the magnet || The dial now deflects in the positive direction. The electrons move downward. ||
 * 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 || Same thing happens as above. ||


 * 1) ** Induction With an Electromagnet: ** Click on tab called //Transformer//.
 * 2) 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.


 * 1) 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.


 * 1) 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.


 * 1) Reverse the current in the smaller coil, by moving the slider on the battery all the way to the left. Repeat Step b.


 * 1) 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.


 * 1) Increase the magnitude of the power supply by moving the slider on the left side of the power supply up. Repeat Step b.


 * Observation-Part II**
 * Experiment || Observations ||
 * Move the smaller coil inside the larger coil || The voltmeter dial deflects in the negative direction and the electrons move. ||
 * 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 || The voltmeter dial deflects in the negative direction, but less than before. The electrons move. ||
 * Reverse the current in the smaller coil, by moving the slider on the battery all the way to the left. Repeat Step b. || The voltmeter dial deflects but in the positive direction now. ||
 * 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 || The voltmeter dial deflects back and forth from positive to negative. Electrons move back and forth. ||
 * Increase the magnitude of the power supply by moving the slider on the left side of the power supply up. Repeat Step b || The dial deflects as above, but a lot more now. Electrons move back and forth. ||

Based on your observations from the first part of the lab, did the speed of the motion have any effect on the galvanometer?
 * Discussion Questions: **
 * Yes, the faster the magnet is moved through the coil, the farther the arrow on the voltmeter will move (the larger the voltage).

In the first part of the lab, did it make any difference whether the coil or the magnet moved?
 * No. The voltmeter deflected the same amount in the same direction.

Explain what the voltage meter readings revealed to you about the magnet and the wire coil.
 * The voltmeter readings showed that when the magnet is brought in proximity with the coil, it causes an electric pressure difference in the coil resulting in the electrons flowing.

Based on your observations, what conditions are required to induce a current in a circuit?
 * The magnetic field must be present and the object must be moving in order to induce current.

Based on your observations, what factors influence the direction and magnitude of the induced current?
 * Angle, Magnetic Field Strength, and Velocity determine the magnitude. Alignment determines direction.


 * Conclusion**

Some of my hypothesis was correct. The faster the object moved, the larger the deflection of the voltmeter dial, indicating stronger current. Also the stronger the magnetic field, the larger the current. However, it was not possible to test the angle or the area in this experiment.