Phys1120 Post Exam 3 Review

Phys1120 Post Exam 3 Review:

Inductors

F M = L I (Definition of L)

d I dF M d I E= - L (from M = L I , = L + Faraday's Law) d t F d t d t

LR circuits:  I thru L cannot change instantly  In steady state, I = constant, VL = 0 so L acts like a short.  time constant  = L/R

UM 1 2 Magnetic energy density = uM = = B vol 2m0 1 Magnetic energy of inductor = U= L I2 2

AC Circuits

2 Vpeak V(t) = Vpeak sin(t), V= V = rms 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 V P N P

IS VP N P Pout = Pin  IS VS = IP VP  = = IP V S N S

EM Waves

 Light is an electromagnetic wave which is created by accelerating electric charge.

 Know what a plane wave is.

 l f= c = speed of light = constant , EM spectrum (radio, visible, IR, UV, etc)

power P  intensity (W/m2 ) = , I = area A

Phys1120 Notes, Dubson ©University of Colorado at Boulder RF-2

Ray Optics c  Snell's Law: n1 sinq 1= n 2 sin q 2 , where index of refraction = n = v

o n1 sinq c= n 2 sin(90 ) = n 2  total internal reflection, critical angle C : 144424443 1  Converging and diverging lenses , focal length

f > 0 f < 0  Ray diagrams, image formation, real vs. virtual images

 Camera vs. eye

1 1 1 h d  image/object math: = + , M � i i f do d i ho d o

Phys1120 Notes, Dubson ©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.