Physics 6B
Spring 2014
Practice Final
1) A long horizontal wire carries a current of 56 A. A second wire made of copper
(density 8.90103 kg/m3) with a diameter of 2.0 mm is suspended magnetically 4.50
cm below the first wire as shown in Figure A.
a) What
RWA Draft #3
QUESTION:
Why does the turntable spin faster when we pull the weights inward?
A real world application of our demo is the slanted spinning turntables found on many playgrounds.
Rather than have a bar in the middle of the turntable where one c
Electric Field Lines Dipole
The charges are
equal and opposite
The number of field
lines leaving the
positive charge
equals the number of
lines terminating on
the negative charge
Magnetic Fields
A vector quantity
Symbol
B
Direction is given by the d
F1=I1lxB2
Force on wire 1 due to wire 2
0 I 2 0 I1 I 2
F1 =I1 B2 =I1
=
2a 2a
F1 0 I1 I 2
=
2a
The same force by wire 1 to wire 2 has the
same magnitude but opposite direction, thus
in general
F 0 I1 I 2
=
2a
Ampere s Law
The product of B ds can be ev
Coulomb s Law
Fe = ke
Q1 Q2
r
Magnitude
2
The SI unit of charge is the Coulomb, C
ke is called the Coulomb Constant
ke = 8.9875 x 109 N.m2/C2 = 1/(4)
is the permittivity free space
= 8.8542 x 10-12 C2 / N.m2
Note the similarity to Newtons law of gra
EXTRAORDINARY PHYSICAL PROPERTIES:
Field Due to a Plane of Charge
A
and E =
E = 2EA =
2 o
o
E = Q/0A.
Vba = Qd/0A.
Parallel Plate Assumptions
The assumption that the electric field is uniform is valid in
the central region, but not at the ends of the pl
Resistor = conductor with resistance R
L
R = 1/ L/A
A
= conductivity
(material constant)
(-1 m-1)
Sea water: 5 -1 m-1
Tap water: 0.05 -1 m-1
Deionized water: 10-5 S/m
(insulator)
The higher the more current will flow for a given voltage and shape
Simple
Midterm 2 info
When:
Where:
Friday, May 15, 9 am (in class)
Humanities A51
Material covered:
everything covered after midterm 1 and until Monday 5/11:
Electric charge and field,
electric potential and energy,
Capacitors and dielectrics,
Gausss law
For
Damped oscillation
Damped oscillation in car suspension
damped springs
Automatically closing door =
critically damped spring oscillator
Swing door =
Underdamped oscillator
Swing = damped, forces oscillator (pendulum)
Driven oscillator
Small b
large b
0
A
Equipotential Surfaces
Potential energy is constant along
equipotential surfaces: no work done.
The Van de Graaff Generator
A Van de Graaff generator can be
used to achieve very high
potentials.
Breakdown electric field in air
is ~3 106 V/m, so a 1-m
r
n=1
n=2
n=3
n=4
n=5
n=6
What does a sound wave look like ?
343 m/s
Eardrum is a driven (forced, damped) oscillator!
Spherical sound wave
Violin
Driven oscillator
4 strings
bow
soundboard
horsehair
Flute
xactly twice the frequency of the first
.
WOLLEF ,PP
Doppler effect
Ocean waves:
Period T0 10 s ; 5me between
two waves (crests)
Boat running with waves
(velocityboat < velocitywave):
T > T0 or f < f0
Doppler shiF
Surfer riding wave:
(velocitysurfer = vel
Faraday s Experiment
Set Up
A primary coil is connected to
a switch and a battery
The wire is wrapped around
an iron ring
A secondary coil is also
wrapped around the iron ring
There is no battery present in
the secondary coil
The secondary coil is
Midterm #2
Physics 68
-
David Schriver
February 23,2015
S-
Name:
Please do the
necessary
t'fi*l
Student I.D.#
following 4 problems. Show all work and reasoning. Use the back of the page
*[email protected]"[email protected]
final aqswer.
Problem #
Score
1
?r
2
2r
3
)"r
4
Total
)r'
Midterm
Physics 68
-
#L
David Schriver
January 26,2015
Name: 5 " t;lr,o*r
Student I.D.#
Discussion Section:
Please do the
necessary
following 4 problems. Show all work and reasoning. Use the back of the page if
andCiilid
o.l
uo*lyo.n final answer.
Problem
Physics 6B Fall 2015 November 13, 2015 Dr. Shoko Sakai
Midterm #2
YOUR NAME:
DISCUSSION SECTION:
YOUR ID:
Please write your answers clearly.
Partial credits are given, so show as much work as possible. You may use diagrams
where appropriate.
You are
Physics 6B
Midterm 2 Review
Check all end-of-chapter summaries
Review lecture notes
Study worked examples
Chapter 21
Two types of electric charge, positive (+) and negative (-)
Like charges repel, unlike charges attract. Charge is conserved.
Objects can b
Physics 6B
Midterm 1 Review
Chapter 14
Any vibrating system in which the restoring force is
proportional to the negative of the displacement, F = -kx
(Hookes Law), will oscillate in simple harmonic motion
with period T and amplitude A (ignoring friction)
E
r
Some circuits cannot be broken down into series and
parallel connections. For these circuits we use the so
called Kirchhoff s rules.
V = 0
closed
loop
I1 I2
I3
Problem Solving: Kirchhoff s Rules
1. Label each current, including its direction.
2. Ide
EXTRAORDINARY PHYSICAL PROPERTIES:
Field Due to a Plane of Charge
A
and E =
E = 2EA =
2 o
o
E = Q/0A.
Vba = Qd/0A.
Parallel Plate Assumptions
The assumption that the electric field is uniform is valid in
the central region, but not at the ends of the pl
Physics 68 - Fall Session 2013
PRACTICE FINAL
2 page notes and calculators are permitted
Problem 1.
A ZOO-g block is attached to a horizontal spring and executes simple harmonic
motion with a period of 0.250 s. The total energy of the system is 2.00 I, nd
Electric eld and conductors
E-eld inside conductor is zero (when charges are at test)
Any net charge on a conductor distributes itself on the surface
The electric eld is always perpendicular to the outside surface
*eeindlmiu Conu mats u. war-H4 up,
c'myr on Sin-J atom
_ " ",Il .' 1"
gvdmce FiNAL as -=- Conccpiaai
For-questions lAiegr'orrpofdettedmnwsrepresentselech'iceldlines.
Whetisthedirection, ifany,oftheforeeanthepartlcleduetotheeldi£.
theparticieisinitially
Discussion 8
6B Spring 2015
1.
ID and Role _
Discussion TA and Time _
(Exam Level) An RC circuit can model some of the
electrical characteristics of a cell membrane. (You
can use a calculator to get through it faster.)
a.
A cylindrical capacitor (like the
