Week 4
News
Midterm (Feb 11) will cover material taught upto and including Friday
Feb 6th.
So for sure Chapters 42, 21, 22, 23 and possibly parts of
Chapter 24
Section 203 writes Thur Feb 5th 11:00 to 12:20
The Practice Session on Monday Feb 2(5:00 to 7:00 in Hennings 200) will be
a closed book tryout of last year's Section 203Midterm. The exam will
then be taken up by Dr Fameli - please see his web-site for more details:
http://www.physics.ubc.ca/~fameli/p102
Resource centre will be set-up next week Thursday 12:00-2:00 and will run
every week
A sample midterm has been handed out - numerical answers to the questions
are given.
On Monday we will finish Gauss' Law and will start Chapt 23 - Potential.
It would be a good idea to skim through this chapter to refresh your memory
concerning electric potential and electric potential energy.
Homework comments:
Chapt 23 P 43
a) is there any charge contained inside the sphere?
b) you can determine the electric field due to the point change at any point,
you simply need to know the distance from the point charge.
Chapt 23 P47
To construct the object you can take:
- a uniformly charged outer sphere of radius ro, on Monday, you
know how to find the electric field anywhere due to that changed sphere.
- a smaller uniformly charged sphere of radius ro/2 with charge density
the same magnitude but opposite sign as the one above. - again you can determine
the electric field due to this
The electric field of the composite object at any
point will just be the vector sum of the the fields due to the separate spheres.
I hope this helps!
Answers to in class problems
Ex 21.6 -574 i N, -5.75x10-7 i N ,
+1.15x10-6i N
Ex 21.7 +8.8x1014 m/s2, 5.0x10-9s,
0.011 m
Ex 22.1 a) Zero flux since theta is 90 degrees. b) 17.3 Nm2/C
Ex 22.2 Total flux through whole cube is zero - from
GL would expect this since the cube
contains no net
charge.
Ex 22.3 -1.28x10-10 C/m2, +9.6x10-11C/m2,
14.5 N/C, 10.8 N/C
Ex 22.4 Inner surface -2x10-6 C, outer surface +12x10-6
C