Physics III Exam

true

true or false: at the atomic level— SN poles still exist?

Force on a moving charge in the magnetic field

velocity selector equation

• m/s

velocity selector

the particles do not dip or rise bc the electro + mag forces balance

true

• 0.5 T is strongish

true or false: 1 tesla is a strong magnet

1 T =

equate centripetal to magnetic force equation

mv²/r = qvB

• charge

• mass

• speed

• strength of mag field

what does radius depend on?

relationship between the radius of a charged particles trajecotry in a mag field

r=mv/qB

mass spectrometer

method used to identify samples of unknown origin

magnitude formula

permeability of free space

μ0

ture

true or false: two wires can repeal or attract

true

true or flase: magnetic field is not r² dependent

force per unit length of wire

they will attract each other

currents flowing in the same direction will attract or repel each other?

repel

currents flowing in opposite directions will attract or repel each other?

flux

the amount of magnetic field lines going through a patricular area

Tm²

unit of flux is___

true

true or false: when you gain flux then a current is generated in the opposite direction

• charge

• mass

• speed

• strength of the mag field

what does radius depend on?

bc it is harder to move/accelerate

m2>m1

why does a bigger mass = a bigger circle/trajectory?

to fix v so that the radius of the path is proportional to mass

what does a veloctiy selector do in a calutron?

the number of circuits and intensity of current

what does the magnetic field of a solenoid depnd on?

the field outside is weaker and divergent

what area of the field is weaker in a solenoid?

stronger, uniform

long solenoid = ____ and ___ magnetic field

dipole magnet, not as uniform

short solenoid magnetic field looks like a ___ and is not as ___

Faraday’s law of induction

Lenz’s Law

the minus sing of faraday’s law of induction means

lenz’s Law

the emf creates a current I and magnetic field B that oppose the change in flux ΔΦ

• lose flux to the right and the new current and other loop will generate magnetic field lines of its own in opposite direction

N pushed towards the current = gaining positive flux → current creates negative flux to conserve energy (counter current)

N side is pulled away (to the left) = loop loses pos flux → the current generates more positive counter flux = moves to the right

S is pulled toward the current = gaining negative flux (moves leftward)→ coil makes positive counter flux to the right

n̂

indicates whether flux can be positive or negative

Inductance (L)

generates counter current + depends on the current changing

• not stable

volts x seconds/ amperes

units of inductance (L)

capacitor

• potential energy

½ x 1/c x Q²(t)

inductor

• kinetic energy

½ x LI²

(ΔQ/Δt)²

kinetic energy of oscillating system

Q(t)=Q(0)cos(ωt)

the charge on a capacitor in an LC circuit equation

Capacitor

stores E in electric field

Inductor (L)

stores E in magnetic field

v(t)= -ωx0sin(ωt)

x(t)= x0cos(ωt) is complimentary to

v(t)=ωtx0cos(ωt)

x(t)= x0sin(ωt) is complimentary to

v(t)= ωx0sin(ωt)

x(t)= -x0cos(ωt) is complimentary to

v(t)= -ωx0cos(ωt)

x(t)= -x0sin(ωt) is complimentary to

E and B

radiation is the motion of ____ and ____

c= λf

wave equation

red

orange

yellow

green

blue

indigo

purple

low to high frequency (colors)

gamma rays

x-rays

ultraviolet wave

infrared waves

radio waves

high to low frequneices of rays

• faraday’s Law of induction describes the emf or potential difference produced by a changing mag field

• a potential difference can be related to an electric field = changing a mag field produces an electric field

  • vice versa

what did maxwell discover?

maxwell’s equation spatial variations

maxwell’s equation temporal variations

• square of the fields B + E

  • on a volume basis; u

    • how momentum + energy are transported across spacetime

energy in a field is ____

energy density equation

electromagnetic waves move like ocean waves

• maxwell

luminiferous ether

• E always ⊥ B

• E can be oriented in any direction in the y-z plane

  • B oriented with it

3 aspects of the polarization of light

polarized light

Restricting the E field to being parallel to a given axis (polarization axis)

• B field is polarized too + 90 degrees away

• incoming light polarized vertically

• light pass thru his sample

• came out polarized a few degrees out of vertical

• tldr optical roation

pasteur studied tartaric acid’s effect on polarized light and found that

the theoretical black body

the perfect absorber and emitter of radiation

• the quantum of energy and his constant h

  • explained why those sepctra peak

  • began the quantum science revolution

Max Planck’s new theory of black body radiation introduced ___

• circular shape

• slope angle can vary from steep to very gradual

• they are like a stack of circles of steadily increasing radius

• for a “right cone” the symmetry axis for the stack of circles is perpendicular to the plan of each circle

what do you know about cones?

clockwise

• it is losing inward flux → needs more = thumb points inward = clockwise current

flux goes deeper into the neg so that change in flux is < 0

room temp: 295 K

sun temp: 5800 K

room temp and the temp of the sun in Kelvin

emf induced by an inductor

ground state: n=1

excited states: n = 2,3,4

ground state vs excited state

quantum theory

only a few orbital levels of hydrogen are allowed

• electrons only live at certain specific “altitudes” & no others

H-alpha photon

when the electron de-orbits from n=3 to n=2 it loses energy which goes into a photon

Quantum theory of hydrogen

as an electron drops to lower EPE orbit, it emits a photon w/ missing energy

• E=ħω

false

true or false: an electron can drop lower than it’s ground state

• only the assumption of specific quantized oscillation would fit the data

  • E=hf for an oscillator of frequency f

  • einstein said ditto for photons

Planck’s quantum of energy proposed

only certain orbits and ħ allowed = why the f and λ are quantized

Planck’s quantum of energy concluded

smallish atom: constructive interference and diffraction is observable

realllyyyy small atom: diffraction effecrs will not be observable as you pull it out of your pocket

smallish atom vs realllyyyy small atom

you get small inerference which is not observable

if the opening is much much larger than the wavelenth then ____

• ħ

each quantum leap is a jump between ellipses in a phase diagram for the electron and the area decrease or increases by a multiple of ___

orbital size

ħ and λ → selects the ____

hf

orbital size controls ΔEPE which = __