Remember to sign up for the lab

You may now sign up for the lab by writing your name on the list on the door to room V225.

The lab is held during week 45, 46 and 47 at the following times:

Monday and Tuesday: 08 – 12
Wednesday, Thursday and Friday: 13 – 17

Find a time that suits you and sign up on the list. The lab will be pretty much like how it was last year, and you can find this years experiments under the title “Lab-øvelser”:

http://www.uio.no/studier/emner/matnat/fys/FYS1120/h11/

We strongly encourage you to read through the lab exercises before coming to the lab. This way you will get much more out of the exercises and will hopefully understand a lot more of what the experiments actually teach us.

Midterm exam

There came in some questions regarding the relevance of the weekly exercises considering the upcoming midterm exam. The answer is that the weekly exercises of course are relevant and therefore valuable practice. The questions for the exam might include everything that has been lectured up to and including the lecture 04.10 where the main subjects will be electrostatics, currents and magnetostatics. The lecture plan for the semester is found here:

http://www.uio.no/studier/emner/matnat/fys/FYS1120/h11/undervisningsplan.xml

Remember that you can bring an A4-paper with your own notes and allowed mathematical and physics tables (Rottman, Angell/Øgrim og Lian) as well as an approved calculator.

Update: There will be group lessons on Tuesday, 11 October, but no group lessons on Friday, 14 October.

Some missing information in the oblig

As Finn mentioned in today’s lecture, there has been some information missing from the oblig:

The side walls in the well are made of conducting material.

Some of you have already been able to deduce this from that V=0 on the side walls tells us they are in equipotential, and knowing that conductors are equipotentials, the walls are most likely conductors. However, it should have been explicitly stated that they are conducting, since this does not always have to be the case.

Good luck with the rest of the oblig, and remember to attend to the group sessions if you have any questions. If you don’t have the time to attend, you can of course contact us by e-mail or here on the web pages.

The oblig is here

The oblig has been posted on the course pages.

You can find it here under “Obligatoriske oppgaver”.

Please note that last weeks exercises included an oblig warm-up. This can be useful if you want to test yourself with a simpler problem before going ahead with the whole oblig.

In addition, you’ll find the note about Jacobi’s method on this page, under the link named “Numerical solutions of Laplace’s equation”.

You’ll find the due date in the oblig itself.

Good luck!

Electromagnetic java simulations

The java simulations that Andreas Görgen showed in the lectures can be found here:

The two first ones allows you to set up charge distributions and visualize fields, field lines and equipotentials. The third one comes with some preconfigured and interesting charge distributions where you can do things such as taking the flux integral of the field. As a recommendation for link 3 try out; setup: charged plate dipole, mouse: surface integral and see how you change the field by varying the the size of the plates. In one limit you get the familiar dipole field, while in the other you get the field from a parallel plate capacitor.

Postponed lectures

Due to UiO’s 200 years anniversary the lecture last Tuesday had to be postponed and will be held tomorrow in “Store fysiske auditorium” replacing the  planed vector analysis lecture. The lecture on vector analysis will instead be held this Friday in room V329 where the subject will be flux and divergence.

On the concept of dipole moment

The dipole moment of a configuration of charges is an important concept in electromagnetism, but in most introductory texts it might seem like the dipole moment is only defined for two opposite point charges separated by a distance. This is however not the case. The dipole moment can be defined for any configuration of charges where the net charge is zero.

H20 is a polar molecule which means that it has dipole moment. However the H20 molecule is not just two point charges separated by a distance. So how do we then define its dipole moment? Source: Qwerter/Wikipedia

The dipole moment is also crucial in order to undersant how molecules and atoms are affected when they are placed in electric fields as well as understanding the phenomenon of “polarization” of matter.

If you want to learn more about why dipole moments are important and about its generality the following note might be of interest to you: