Friday. II will
today. II will
k Q1 Q2
we have been working with Coulombs Law
this k constant is 9x109
But you will also see it represented like this,
using a different constant.
Ive spared you the units here th
An electron with a speed of 5x106 m/s is launched as
shown into a region with an upward electric field
of 500 N/C. Find yf.
I know many of you got the answer here.
But I wanted to show some details.
Everywhere the electron goes, it
Exam 2 is next Friday. It will cover Ch 21,22, and 23.
So we have a fair amount of time to digest all of
the Gauss Law stuff.
This Lecture 17 has two objectives. One is to go through
the planar non-conducting example posed in Lecture 16.
The other is to g
In the HW for today, you found the
electric field due to the presence of a set
of source charges.
Today we look at the electric field due to
the presence of a continuous line of charge.
This can be done using the Ch 22 stuff that
you have been doing, or i
Lecture 13 closed with a challenging problem.
Non-conducting cylinder with a charge density.
If you were able to get it, youre off to a great
start in your understanding of Gauss Law.
The next few slides should help with your conceptual
understanding of c
A suggestion for todays Lecture 16 is to view it
in Normal mode in PowerPoint instead of in SlideShow.
Certain features show up jumbled in SlideShow and in the
printed version, but things look fine in Normal mode.
We have a flat sheet of non-conducting
In Lecture 11
you did this example
where you found
the electric field
at a point,
with Q = +5x10-6 C.
contributed a vector
field to the point
and we added the
fields as vectors
to find the
Exam 2 this Friday.
It will cover Chapters 21, 22 and 23.
Relevant material can be found in Lectures 9 through 17,
as well as the homework problem found at the end
of Lecture 18.
Two practice exams have been posted on Cobra.
I will have copies of one of t
We have been looking at the magnetic force on a
moving charge. Today we consider a section of wire
filled with moving charges and look to find the
collective force exerted.
The region of the wire is filled
with a magnetic field directed into
on a single charge.
F = Q v x B
on a section of
F = I L x B
Torque on a loop of
= N I A x B
made by a
vS x ^r
We have a negative
Electric force on a test charge
FE = QT E
Magnetic force on a test charge
FB = Q T v T x B
An electron is released from rest and moves through a
potential difference of 150 V.
Find the s
Friday is Exam 3.
It covers Ch 24, 25, 26, and 27.
Practice exams are available on Cobra.
This week we have review in lab (copies of a practice exam
will be available) as well as
the lab assessment on building a resistor network.
In Lecture 11,
Heres a reminder of an exercise
that you did in Lecture 13.
Two charges. Looking for the
electric field produced
at point P.
Electric fields point away from
positive source charges.
Needed vector addition to find the
net rightward field.
So far with Faradays Law, weve been looking at examples
where the magnetic field changed as a function of time
and/or position within the circuit loop.
Today we keep the magnetic field fixed, and look at
situations where the geometry of the circuit loop u
Today we look at a corollary to Faradays Law, called
Lenzs Law. Lenz is a convenient principle to find the
direction of the induced current in a circuit w/o the need
to do any extensive computation.
You will find it valuable in one of two ways. Either to
number of coils
O Eds = - N
= V = I R
curve is the
circuit that receives
the induced current
on the left side
is the voltage
induced in the circuit
surface of integration
is the area enclosed
by the ci
In Lectures 13 and 14, we had this problem.
It would be helpful at this time to go back and review
Slides 2 through 18 in Lecture 14. What comes next
will make a lot more sense if you do.
We have a non-conducting cylinder
of radius R = 1 meter, surrounded
In the homework, youve been
using Coulombs Law to find the
net force on charges.
The 2D vector addition thing is
usually rusty at this point in
142, so the HW theme this
week is to brush up on x and y
In doing #11, you notice that
there were 3
Today we look at a couple of examples that should
help you see how Gauss works for spherical and cylindrical
geometry. Well hold off on the planar case until
Lecture 16, so we have the chance today to settle some
There are many nuances to this Gau
The class average for Exam 1 was 76.8%.
You are eligible to drop your lowest exam of the
semester, provided you have no more than 5
lecture absences during the term.
Also, if you arrive more than 10 minutes late for a
lecture, you will be counted as being
Three practice exams are available on Cobra.
Hardcopy of one will be available at lab this week.
Lab assessment this week on single-variable
Exam Friday (here in M124).
You can start the exam 3 minutes before the hour
and we will finish 53 min
A heat engine is a system
that operates in a
repeatable cycle of
The second law of
thermodynamics states that
this series of processes
cannot convert fuel into
work with 100% efficiency.
These next three sessions are devoted
Your quiz points accumulate each day.
The first correct quiz submitted by a group earns 3 points, the second earns a
2, and every other correct submission scores a 1. To make it interesting, you
can wager any or all of the points that you have previously
Newtons Law of
G = 6.67x10-11
This week starts the schedule
of lab experiments.
There is no lab manual or notebook
to purchase each week
a packet will be distributed.
You do need to bring a calculator
(preferably a TI) that can do
Your quiz points accumulate ea
to Physics 142
Lets start with something that
may be familiar.
PV = nRT
Otherwise known as
the Ideal Gas Law.
PV = nRT
Pressure can be expressed in a variety of
ways, one being lbs per square inch.
Can you express pressure in
Homework assignments are due at
each lecture session.
HW is not handed in for a grade, but
the quizzes will be related to HW
problems. Its a good idea to keep a
notebook of completed HW problems.
Next week starts the schedule
of lab experiments. I would a
In Lecture 5 we looked at the
constant-pressure and constantvolume processes.
Today we get into the constanttemperature and adiabatic processes.
With the Q and W information from
each of these four, we can quantify
of many physical engines.
Physics 142 Exam One
Consider all data and constants given to be exact numbers.
Show work to receive credit for your answers.
Work answers to 3 significant figures. Remember units.
TK = TC + 273o
cice = 0.53