Generators & Motors (electromagnetism)

In 2013-2014 Mr. Konichek was duct taped to a column in North Commons period 6 as a fund raising activity for FFA.  Thanks for the t-shirt FFA.

If you missed today:  In 2012-2013

1.  We watched a short video (The Core) that explained the magnetic field of the Earth is made by the movement of the outer core (liquid iron/nickel) causes the magnetic field.  It also explained that Earth's magnetic field protects us from very harmful infrared (heat) from the sun.  If the magnetic field wasn't there we would fry.

2.  We reviewed #10 Magnetic field diagrams for four different circumstances and noted that when we grade them we'll be looking for the field lines NOT crossing AND at least ONE ARROW indicating the direction (away from north/toward south) of the magnetic field.  Students done drawing all the magnetic field lines had a bottle with iron filings caught in it and a pvc pipe down the center. 

3.  We reviewed the first seven questions on the homework study sheet and there answers and noted just two more questions remain to cover today.
period 1                period 4            period 5            period 7            period 8

4.  We bent some aluminum nails and left some iron nails straight and used an overhead projector to show there shadows on the front screen (so you could not tell they were different metals).  We proceeded to use a magnet to pick up the straight nails leaving the bent ones behind.  We pretended that the reason the magnet did not pick up the bent nails is because they were bent but it was really because they were aluminum.  Big Picture is that the shape of ferromagnetic substances does not matter, they are magnetic all the way down to the spinning electrons around a single atom.

5.  To answer number 8 on the homework study sheet we explained how a motor works and how a generator works.

Basically, this shows why E&M go together as some person noticed that if you send a current through a wire a magnetic field magically appears in concentric circles around the wire (motor, needs electricity to work) but if you do work to force a wire through a magnetic field a current will magically occur (generator, does not need electricity but makes electricity).  How much electricity you make is directly related to how fast you move the wire through the field, how strong the magnetic field is, the length of wire cutting the magnetic field, and the angle you cut the field at (90 degree angle makes the most electricity). 

Note in the first right hand rule diagram that if you point your right hand thumb in the direction of the current (direction a positive charge would flow, toward the negative/away from the positive of the battery) your fingers curl in the direction of the magnetic field (picture arrows at your finger tips).  Or if you curl the wire around a nail (conductor) and send a current in circles around the nail - the nail will temporally become a magnetic.  As long as the current is flowing the domains align and the nail becomes a magnet but when the current is shut off the domains return to canceling each other out so return to not being a magnet.

6.  To show how a motor can become a generator and a generator can become a motor we passed out the gen-cons.  Note the videos below. 

7.  One of the coolest demonstrations today is Lenz's Law.  Note the short video below where we dropped a small magnet down a copper pipe and it took a long time to fall out.  The reason why is the falling magnet generates another magnetic field that opposes the original magnetic field (like fields repel thus oppose each other).  Actually, the falling magnet causes electrons in the copper pipe near it move and these moving electrons cause the second magnetic field.  The conservation of energy holds because the work done to lift the magnet equals the potential energy at the height above the pipe equals the current potential energy + kinetic energy + electric field energy + new magnetic field energy.