RF-1
Phys1120 Post Exam 3 Review:
Inductors
ΦM = L I
E= −L
(Definition of L)
dI
d ΦM
dI
(from ΦM = L I ,
+ Faraday's Law)
= L
dt
dt
dt
LR circuits:
•
I thru L cannot change instantly
•
In steady state, I = constant, VL = 0 so L acts like a short.
•
time constant τ = L/R
UM
1 2
=
B
vol
2µ 0
1
Magnetic energy of inductor = U = L I 2
2
Magnetic energy density = u M =
AC Circuits
V(t) = Vpeak sin(ωt),
Vrms = V 2 =
Vpeak
2
All the DC voltage formulas V = I R, P = I V = I2 / R = V2 / R
work OK with Irms, Vrms, and Pavg
V
V
N
Transformers only work for AC voltages only out = S = S
Vin
VP
NP
I
VP
N
Pout = Pin ⇒ IS VS = IP VP ⇒ S =
= P
IP
VS
NS
EM Waves
• Light is an electromagnetic wave which is created by accelerating electric charge.
• Know what a plane wave is.
• λ f = c = speed of light = constant , EM spectrum (radio, visible, IR, UV, etc)
• intensity (W/m 2 ) =
power
,
area
Phys1120 Notes, Dubson
I =
P
A
©University of Colorado at Boulder
RF-2
Ray Optics
• Snell's Law: n1 sin θ1 = n 2 sin θ 2 , where index of refraction = n =
c
v
o
sin(90
• total internal reflection, critical angle θC : n1 sin θ c = n 2 ) = n 2
1
• Converging and diverging lenses , focal length
f >0
f<0
• Ray diagrams, image formation, real vs. virtual images
• Camera vs. eye
• image/object math:
1
1
1
,
=
+
f
do
di
Phys1120 Notes, Dubson
M ≡
hi
d
= i
ho
do
©University of Colorado at Boulder
RF-3
Are you ready for the Final Exam?
If so, you should know and understand.
•
The definition of the electric field.
•
The definition of the magnetic field.
•
Coulomb's Law.
•
The E-field due to a point charge and how to derive it.
•
Gauss's Law.
•
The definition of electric flux and magnetic flux.
•
The definition of voltage difference.
•
Voltage due to a point charge and how to derive it.
•
The definition of capacitance.
•
Kirchhoff's Laws for circuits (voltage law and current law)
•
The Biot-Savart Law.
•
Gauss's Law for B-fields.
•
Faraday's Law.
•
The definition of inductance.
•
Snell's Law.
You should invent a problem in which you use
To prepare for any exam:
•
Study the online lecture Notes.
•
Review Concept Tests, CAPA problems, and Tutorial HW. (Read question and
try to remember reasoning that gets to the answer)
•
Prepare your formula sheet. Prioritize: which are the important equations?
•
Take the practice exam.
•
It is no good to memorize answers. You have to understand and remember how
you got the answers.
Phys1120 Notes, Dubson
©University of Colorado at Boulder