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!!!!!!!
Monday, March 18, 2019
Saturday, March 16, 2019
Back off - The College one goes to DOES NOT matter!
A really important article for all of us in the high schools - two broad studies were carried out by a mathematician and economist, where they looked over years of data for college graduates, and looked at careers, incomes, and happiness with one's life after college graduation. The results were pretty clear, that it made no difference where one went to college! Going to Harvard or Stanford does not, on average, lead to more money or more happiness than less elite colleges.
This follows other important statistics, such as teens are presently the most stressed population in our society, and by far the biggest stressor is school and our near demands that every teen must go to college if they want to have any chance at having a life worth living. And the pressures to get nothing but A's while taking 6 AP classes and being in every possible club, sport and performance, have increased stress levels, led to record levels of depression and anxiety, and record high cases of teen suicide. We must take it easier on our children, and especially on our teens!
Goals are important, hard work is important, school and learning are important. But life must still be worth living, and happiness is still something that is vital for each of us. And the statistics of this college study are an important piece of all this that we adults should take seriously.
This follows other important statistics, such as teens are presently the most stressed population in our society, and by far the biggest stressor is school and our near demands that every teen must go to college if they want to have any chance at having a life worth living. And the pressures to get nothing but A's while taking 6 AP classes and being in every possible club, sport and performance, have increased stress levels, led to record levels of depression and anxiety, and record high cases of teen suicide. We must take it easier on our children, and especially on our teens!
Goals are important, hard work is important, school and learning are important. But life must still be worth living, and happiness is still something that is vital for each of us. And the statistics of this college study are an important piece of all this that we adults should take seriously.
Tuesday, March 5, 2019
Tuesday, March 5
With apologies and frustration, I cannot join you today. Please try the following:
Period 3-4, 8-9
Complete the chart we began yesterday by checking out this introductory video on rotations. Then, check out how to find torque and equilibrium. Take some notes on the examples, and then you can break into groups to try and complete the practice problems below. Tomorrow we will get into a lab where you can see all the rotational quantities in action.
Ch. 9 #3, 5 on page 5
Ch. 10 #1, 2 on page 7
Ch. 11 #13 on page 7
Period 5
Static electricity labs should be done and turned in.
Using what we were saying about induction and polarization yesterday and last week, in small groups try and complete the first three pages of the static electricity packet. These include the vocabulary and chart of insulators and conductors for the first page, rule of electric charges for the front and back of the second page (attraction and repulsion), and charging by induction for the front and back of the third page. For extra credit, try the fourth page that deals with lightning. Feel free to use either video from the E-day (video 1, or video 2). If you try the lightning page, it will ask about the electric force between charges. There is a formula that looks and behaves like the formula we used for gravity. This is:
F = kQq/d^2
The k is a number, k = 9 x 10^9 = 9,000,000,000 (9 billion). The Q,q are symbols for electric charge, which has a unit called a coulomb, C. Notice it is divided by distance-squared, just like gravity. If charges are twize as far apart, the electric force is 2^2 or 4 times weaker, etc.
Answer keys for the packet is in the Electricity folder on our school website.
Period 3-4, 8-9
Complete the chart we began yesterday by checking out this introductory video on rotations. Then, check out how to find torque and equilibrium. Take some notes on the examples, and then you can break into groups to try and complete the practice problems below. Tomorrow we will get into a lab where you can see all the rotational quantities in action.
Ch. 9 #3, 5 on page 5
Ch. 10 #1, 2 on page 7
Ch. 11 #13 on page 7
Period 5
Static electricity labs should be done and turned in.
Using what we were saying about induction and polarization yesterday and last week, in small groups try and complete the first three pages of the static electricity packet. These include the vocabulary and chart of insulators and conductors for the first page, rule of electric charges for the front and back of the second page (attraction and repulsion), and charging by induction for the front and back of the third page. For extra credit, try the fourth page that deals with lightning. Feel free to use either video from the E-day (video 1, or video 2). If you try the lightning page, it will ask about the electric force between charges. There is a formula that looks and behaves like the formula we used for gravity. This is:
F = kQq/d^2
The k is a number, k = 9 x 10^9 = 9,000,000,000 (9 billion). The Q,q are symbols for electric charge, which has a unit called a coulomb, C. Notice it is divided by distance-squared, just like gravity. If charges are twize as far apart, the electric force is 2^2 or 4 times weaker, etc.
Answer keys for the packet is in the Electricity folder on our school website.
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