Electromagnetism

This unit is very similar to the Electrostatics unit in a lot of ways, but the most obvious difference is you can have a single charge (eg. a proton) but you can't have a single pole (magnets always have a north and south pole). We say magnets always come in dipoles.

Please watch the following 2 videos:

• This is a very cool video using ferrofluid and a HUGE magnet. Notice how the liquid follows the magnetic field lines in 3 dimensions! It's too easy to mistakenly picture fields in 2 dimensions in this course.
  • https://www.youtube.com/watch?v=L8cCvAITGWM
• This explains magnetic fields and some of the ways we notice them in the world around us.
  • https://www.youtube.com/watch?v=IgtIdttfGVw (Watch until 4:45)

Then, complete your quiz through Teams. We will have tutorial on Thursday this week at 1:00 pm. Message me if you have any questions .

Magnetic Fields Quiz Key

-Coming Wednesday May 6th at 3pm :)

Good morning Physics 12 students!

Earlier this week we discussed how magnetic fields can come from magnets (iron, nickel, etc...) or from a current carrying wire. Well, if a current carrying wire creates a magnetic field, it would make sense that it can act as a magnet and be attracted/repelled just like a magnet! Today we will be discussing how to calculate the force on a current carrying wire (pretty easy, just one formula) and the direction of that force (less easy, but very important).

Please watch this video which not only goes into detail about calculating the force on a wire with examples, but also goes into detail about the cross product used to calculate the direction of the force. "Cross Product" is actually an extremely important mathematical concept that you will see MANY times if you are going into science or engineering, so while it may seem a bit confusing now, it is well worth your time to understand it. If you are not going into science/engineering, just make sure you understand the formula F = BILsinθ, as well as the right hand rule. It's also important to know that an X represents something going INTO the page while a dot represents something coming OUT of the page.

https://youtu.be/nv28Cp-ILJ0 (please watch thoroughly)

https://www.youtube.com/watch?v=lKEt5bvn7LU (optional - more right hand rule examples)

Note - we now know TWO right hand rules.

• The one we learned on Tuesday (point your thumb along current, curl your fingers along B) gives us the direction of a magnetic field around a current carrying wire.
• The one we learned today (point thumb along current, point fingers along B, palm points to F) gives us the direction of the force on a current carrying wire.
• I know this is a bit overwhelming but you will get used to it if you practice a bit!

Optional - One of the main requests in the recent feedback was for more practice problems. Below is the ultimate review package for you to use as a resource. The relevant problems today are #1, 10, 11 (tricky), 14, 15, 25, 29.

25 and 29 are pretty regular problems if you want something clean to practice.