Recall, 1110,
A. F=ma (e.g., Fgravity) a = dv/dt, etc.
B.
OR
Potential Energy, Work, Conservation of Energy
dW = Fdx.
Recall, 1110,
A. F=ma (e.g., Fgravity) a = dv/dt, etc.
B.
OR
Potential Energy, Work, Conservation of Energy
dW = Fdx.
OK so now in 1120:
Comments re Potential:
1) Potential = voltage is independent of test charge
2) Potential is a property of space, created by
all other charges.
3) Potential is larger (more positive) near positive
charges.
4) E-field points from high potential to low poten
Potential 15
An proton is carried from point i to point f at
constant speed. . The work done by the
external agent is
i
40V
f
100V
15V
A: +85 eV
C: >+85 eV
100V 40V
B: -85 eV
15V
D: Between 0 and +85eV
E: not enough information given
First midterm: averag
Exam Thursday Feb 6 7:30-9:00 pm.
There is no make-up exam.
See website for where your section takes exam.
Special exam circumstances, you should have
had an mail from Prof. Schibli.
Early (6:00 p.m.) exam - cancelled.
Review session, Tuesday Feb. 4, 4-6
Charge 11
CAPA due tonight at 10:00 pm.
No class on Monday (MLK day)
Read Wolfson 20.4, 20.5 for Wednesday
Prelecture Electric Field due Wednesday
Last time: charge. Polarization.
This time: Coulombs Law, electric field.
What materials can be charged?
A.
Gauss 3a
A sphere of radius R has a total charge +Q
spread uniformly throughout its volume.
What is the total charge
R
enclosed by the small
centered sphere of
radius r?
r
A: Q 4 r3
3
r2
B: Q 2
R
r3
C: Q 3
R
E: None of these
R3
D: Q 3
r
Exam Thursday Feb
Last time: E-field integrals, field lines.
This time: Flux. maybe Gausss Law
1. See website for prelectures, CAPAs, and
tutorial HW (the latter due tomorrow).
2. Midterm coming 7:30 pm Thursdsay Feb 6.
Locations to be announced.
3. Clicker questions with
electric field 45
Semi-infinite line of uniform charge density l:
-h
x
0
dq= l dx
Q: What is at x=0?
=
=
2
Discuss with your neighbors.
First what direction does the field point, at x=0?
Then what is magnitude of total field. How you might
set up t
Eflux47
Closed blobular
surface (C.B.S.)
B
Q
The net flux through sphere B is 4pkQ.
What is net flux through the C.B.S. as drawn?
A. 0
B. 4pkQ
C. >4pkQ
D. <4pkQ
E. Cant tell from diagram
Last time: flux
This time: Gauss Law.
Midterm Thursday Feb. 6, 7:30-
ElectricField44
In the four separate scenarios, F indicates the direction
of the force from charge Q on test charge q. E
indicates the direction of the electric field from Q
measured at the location of q. Which of the four
scenarios get the directions of
Last time: Logistics. Review of Physics 1110.
This time: Charge. Polarization. Coulombs Law (?)
Assignments:
Prelecture Coulombs Law was due this morning at 10:00 a.m.
First CAPA set is due Friday at 10:00 pm.
Read Wolfson 20.1, 20.2 for today. 20.3 for F
EM-1
Electromagnetic Waves
Last semester, we studied Classical Mechanics. The fundamental laws (axioms) of Classical
Mechanics are called Newton's Laws.
This semester, we are studying a subject called Classical Electromagnetism. There are four
fundamental
Optics-1
Ray Optics (or Geometrical Optics)
In many circumstances, we can ignore the wave nature of light and assume that light is a stream
of particles that travel in straight lines called rays. For instance, if a light wave from a point
source passes th
AC-1
Inductors, Transformers, and AC circuits
Inductors
An inductor is simply a coil of wire. Inductors are used in circuits to store energy in the form of
magnetic field energy.
Important point: The magnetic flux B through any loop is proportional to the
24-1 (SJP, Phys 1120)
Electric flux, and Gauss' law Finding the Electric field due to a bunch of charges is KEY! Once you know E, you know the force on any charge you put down - you can predict (or control) motion of electric charges! We're talking manipu
F-1
Faraday's Law
Faraday's Law is one of 4 basic equations of the theory of electromagnetism, called Maxwell's
Equations. We have said before that
charges makes electric fields. (Gauss's Law)
currents make magnetic fields. (Ampere's Law)
This is the trut
BII-1
Currents make B-fields
We have seen that charges make E-fields: dE =
1 dQ
r.
4 0 r 2
Currents make B-fields according to the Biot-Savart Law: dB =
0 I d r
4
r2
where 0 = constant = 4107 (SI units).
dB is the element of B-field due to the
I
element o
B-1
Magnetism: a new force!
So far, we've learned about two forces: gravity and the electric field force.
E=
FE
,
q
FE = q E
Definition of E-field
kQ
r2
E-fields are created by charges: | E | =
E-field exerts a force on other charges: FE = q E .
E
The gr
RC-1
RC Circuits
An RC circuit is a circuit with a resistor (R) and a capacitor (C). RC circuits are used to
construct timers and filters.
Example 1. Very simple RC circuit: a capacitor C, charged to an initial voltage V0 = Q0/C,
attached to a resistor R
I-1
Electric Currents and Simple Circuits
Electrons can flow along inside a metal wire if there is an E-field present to push them along
( F = q E ). The flow of electrons in a wire is similar to the flow of water in a pipe.
Definition: electric current I
Crkt-1
More Circuits
In an electrical circuit, circuit elements such as resistors and batteries can be connected together
in series or in parallel. Resistors in series are connected like links in a chain; resistors in
parallel are side-by-side, like so:
i
V-1 of 9
Voltage ( = Electric Potential )
An electric charge alters the space around it. Throughout the space around every charge is a
vector thing called the electric field. Also filling the space around every charge is a scalar thing,
called the voltage
C-1
Capacitors
A capacitor is simply two pieces of metal near each other, separated by an insulator or air. A
capacitor is used to store charge and energy.
A parallel-plate capacitor consists of two parallel plates separated by a distance d, each plate
wi
1 of 10
Gauss's Law
Gauss's Law is one of the 4 fundamental laws of electricity and
magnetism called Maxwell's Equations. Gauss's law relates
charges and electric fields in a subtle and powerful way, but
before we can write down Gauss's Law, we need to in
Q&E -1
Charges, Coulombs Law, and Electric Fields
Some experimental facts:
Experimental fact 1: Electric charge comes in two types, which we call (+) and ().
An atom consists of a heavy (+) charged nucleus surrounded by light () electrons.
nucleus = (+) c
Vectors-1
Vectors
A vector is a mathematical object consisting of a magnitude (size) and a direction.
A vector can be represented graphically by an arrow:
direction of arrow =
direction of vector
length of arrow = magnitude of vector
A vector quantity is