Question

1. click on the electromagnet tab. place the compass on the left - side of the coil so that the compass center lies along the axis of the coil. (the y - component of the magnetic field is zero along the axis of the coil.)
2. move the compass along a semicircular path above the coil until youve put it on the opposite side of the coil. describe what happens to the compass needle.
3. explain the behavior of a compass near a bar magnet and an electromagnet are similar.
4. inside a bar magnets are little magnets. the electromagnet does not have little magnets in it. what causes the magnetic field for an electromagnet?
5. notice the moving blue dots in the wire are moving electrons. use the voltage slider to make the battery voltage 0 v. what happens to the motion of the electrons when the voltage is zero?

b. move the compass around the battery and wire. does the compass move? yes / no
c. is there a magnetic field around a system without moving electrons? yes / no
d. explain why an electromagnet produces a magnetic field?

1. change the current source from dc to ac. an alternating current is changing all the time, what does this do to the magnetic field?

part ii:

1. go to http://phet.colorado.edu/simulation/faraday or google \phet faraday\
2. select the \pickup coil\ tab.
3. make the light bulb light. describe what you have to do to keep the light bulb glowing.
4. to make the bulb light you must have moving electrons. what do you have to do with the magnet to make the electrons move?
5. a generator \makes\ electricity. click on the \generator\ tab.

a. turn on the water. what does the water do to the magnet?
b. turning on the water does cause the light bulb to light, but is water necessary to \make\ electricity? yes / no
c. if there is no water but you have a magnet, a coil of wire, and a light bulb what would you do to make the bulb light?
d. explain and draw a possible set up for what the power company has at the power plant to \make\ electricity for this school.

Explanation:

Step1: Analyze compass movement around coil

When the compass is moved along a semicircular path above the coil from one - side to the opposite side, the compass needle changes its orientation. This is because the magnetic field lines around the electromagnet are non - uniform, and as the compass moves through different regions of the magnetic field, the magnetic force acting on the compass needle changes, causing it to rotate.

Step2: Compare bar magnet and electromagnet

The behavior of a compass near a bar magnet and an electromagnet is similar because both create a magnetic field. In both cases, the magnetic field exerts a force on the magnetic dipole (the compass needle), causing it to align with the magnetic field lines. The source of the magnetic field is different (permanent magnetic domains in a bar magnet and electric current in an electromagnet), but the interaction with the compass is based on the same magnetic force principles.

Step3: Identify source of electromagnet's magnetic field

The magnetic field of an electromagnet is caused by the flow of electric current through a coil of wire. According to Ampere's law, a current - carrying conductor produces a magnetic field around it. The collective effect of the magnetic fields produced by each turn of the coil results in a strong magnetic field similar to that of a bar magnet.

Step4: Analyze electron motion with zero voltage

When the voltage is 0 V, the moving electrons in the wire stop moving. This is because there is no electric potential difference to drive the electrons through the wire.

Step5: Check compass movement around battery and wire

b. When moving the compass around the battery and wire with zero voltage, the compass does not move because there is no current flowing through the wire, and thus no magnetic field is produced by the wire.
c. No, there is no magnetic field around a system without moving electrons. A magnetic field is produced by moving electric charges (currents), and without moving electrons, there is no current and no magnetic field.
d. An electromagnet produces a magnetic field because of the flow of electric current through a coil of wire. The moving electrons in the current create a magnetic field according to Ampere's law.

Step6: Analyze effect of AC on magnetic field

When the current source is changed from DC to AC, the magnetic field produced by the electromagnet changes direction and magnitude continuously. Since an alternating current is constantly changing its direction and magnitude, the magnetic field it produces also changes in the same way.

Step7: Analyze light - bulb in pickup coil

To keep the light bulb glowing in the pickup coil, one must move a magnet relative to the coil. This changes the magnetic flux through the coil, and according to Faraday's law of electromagnetic induction, an electromotive force (emf) is induced in the coil, which can drive a current to light the bulb.

Step8: Analyze generator operation

a. When the water is turned on in the generator, it causes the magnet to rotate. The water flow drives a turbine, which is connected to the magnet, causing it to spin.
b. No, water is not necessary to "make" electricity. Electricity can be generated by any means that causes a change in magnetic flux through a coil, such as mechanical rotation of a magnet by other means (e.g., wind, steam).
c. If there is no water but a magnet, a coil of wire, and a light bulb, one can manually rotate the magnet relative to the coil to change the magnetic flux and induce an emf to light the bulb.
d. A possible setup for a power company to "make" electricity for a school could involve a large - scale turbine (driven by steam, water, or wind) connected to a large electromagnet. The rotating electromagnet is placed near a large coil of wire. As the magnet rotates, it changes the magnetic flux through the coil, inducing a large emf and current, which can be transmitted to the school through power lines.

Answer:

1. The compass needle changes its orientation as it moves along the semicircular path above the coil due to the non - uniform magnetic field of the electromagnet.
2. Similar to a bar magnet, the compass needle aligns with the magnetic field lines of the electromagnet because both exert a magnetic force on the compass needle.
3. The magnetic field of an electromagnet is caused by the flow of electric current through a coil of wire.
4. a. The electrons stop moving. b. No. c. No. d. Due to the flow of electric current through a coil of wire.
5. The magnetic field changes direction and magnitude continuously.
6. 1. Move a magnet relative to the coil. 2. a. The water causes the magnet to rotate. b. No. c. Manually rotate the magnet relative to the coil. d. A large - scale turbine (driven by steam, water, or wind) connected to a large electromagnet near a large coil of wire.