The rest of the week

Below are some things to work on Wednesday - Friday, and then get a well-deserved break before we start the last quarter!

Wednesday (3/20)
Periods 3-4, 8-9:
We're going to try to pick up as much as possible about Faraday's law of electromagnetic induction. This is one of the biggies in all of science, not just physics. It is responsible for understanding electric motors, electric generators, transformers (which make our power grid work properly), different types of stoves and amusement park rides, all the way down to how light works as an electromagnetic wave! There's a lot of applications with a relatively basic observation:

If one changes magnetic flux, flux = BA, through a conductor, voltage is induced. This induced voltage is sometimes called emf (electromotive force). It was discovered by Michael Faraday in the 1820s and 1830s.

emf = d(BA)/dt

This is a video for moving a loop of wire through a magnetic field. This is the case emf = B dA/dt. To get the essence of this phenomenon, also check out a video on what happens just by moving a piece of metal through a magnetic field...it polarizes, and can act like a battery!

In the B dA/dt packet, try the 1981 AP Problem on page 7 and the glider problem on page 8.

Period 5:
Get your data for the resistance lab. This means NOT connecting the circuit to a power supply. Try to set up all the various circuits on your breadboard, and measure the total resistance (set your multimeter to ohms,  ) for series, parallel, and combinations of the two. The big goal is to look for patterns - how does the total resistance change as you put in other resistors? Does the total increase or decrease? By how much does the total resistance change as you add in more resistors? Use the data page as a guide of what each circuit should look like.

Thursday (3/21)
Periods 3-4, 8-9:

This is video for a loop falling through a magnetic field - the magnetic forces act like air friction, and with gravity we get terminal velocity! This is another case of emf = B dA/dt.

Use the example of the video to try the 1990 problem on page 9 and 'the hardest ever' on the last page.  

Period 5:
Today, connect the power supply to the circuit using the short wire jumpers connected in the breadboard. Try the two experiments on the Ohm's law lab sheet. Have a fixed resistance on the breadboard and vary the voltage to measure the currents (in milliamps). Then, change the resistance on the breadboard and set the voltage to the same value each time, to see what effect resistance has on the electric current.


Friday (3/22)
Periods 3-4, 8-9:

This is a video for the second case of changing magnetic flux, where the metal loop stays still and the magnetic field changes. Physically this happens because a changing B-field induces a circulating electric field! This is the reverse of a changing E-field, due to moving charges, inducing a circulating magnetic field. Also watch this video going through an example of circulating E-fields created when there is a changing B-field.

The problems are in the new AdB/dt packet. Try the 2010 and 1978 AP problems on pages 4 and 5. 

Take the past three days as far as you can in class, and we will have time to answer questions, break things down, see physical examples, synthesize and expand after spring break! We'll all figure it out!  :-)

Period 5:
Be sure to complete the data collection for the two labs. When you have all the data, try the analysis questions for each lab, and take things as far as your group can. You will need to make some graphs using the chromebooks for the Ohm's law lab. We will look at the data and go through the big results after spring break! 

HAVE WONDERFUL, RELAXING SPRING BREAKS!!!!!!!