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PHYS 221 exam 2
N/A
77
Physics
03/29/2009

Term
 __ is proportional to the number of field lines passing through a surface
Definition
 strength of field
Term
 South magnetic pole is at the geographical N/S pole
Definition
 N
Term
 General motion in B. Perpendicular v causes ___, parallel v causes ___. Combined, they cause ____.
Definition
 circling, nothing, spiraling
Term
 Net F in a current carrying coil is?
Definition
 zero
Term
 to get torque from a loop
Definition
 superposition lots of tiny rectangles. find torque in each one and add them
Term
 For torque at a moment, when does equilibrium occur?
Definition
 when u=B
Term
 according to ampere's law, how do you calculate an uneven path?
Definition
Term
 Forces between parallel currents. Parallel I's attract or repel?
Definition
 attract
Term
 Longer wire = less/more force
Definition
 more
Term
 Moving a wire in a magnetic field generates?
Definition
 current
Term
 moving a wire causes ___
Definition
 v
Term
 ___ can be described as B cutting through an area (A)
Definition
 flux
Term
 ____ is a law that describes a magnetic field trying to oppose u (dipole moment)... or that an induced u opposes flux
Definition
 Lenz's Law
Term
 Increased number of turns in a coil increases/decreases EMF
Definition
 increases
Term
 AC/DC generators keep switching polarity
Definition
 DC
Term
 flux is always in the same direction of/opposes the direction of B field
Definition
 same
Term
 ____ law describes motion or change in B
Definition
Term
 The flying ring demo demonstrated
Definition
 Lenz's law
Term
 In an alternator or generator, what two variables are constant?
Definition
 B and A
Term
 Larger A = larger/smaller EMF
Definition
 larger
Term
 ___ is when the EMF generated in one coil induces I in another coil
Definition
 Mutual inductance
Term
 ___ is when changing I in a coil also changes flux and therefore EMF
Definition
 Self Inductance
Term
 In a single coil, internal flux is proportional to ____.
Definition
 current (self inductance)
Term
 Compare the inductance of two solenoids, which are identical except that solenoid 2 has twice as many turns as solenoid 1.
Definition
 L2=4L1 ... because increasing N also increases flux = double effect on L
Term
 In a decaying current, coil energy is dissipated in __
Definition
 R
Term
 A generator is a(n) A/C or D/C source
Definition
 A/C
Term
 Where is energy stored in a solenoid?
Definition
 magnetic field
Term
 How are coils and capacitors different from resisors?
Definition
 they don't store E and the don't have phase shift
Term
 Capacitors speed up/slow down current
Definition
 slow down
Term
 Phase shift in capacitor
Definition
 current peak comes before voltage peak -- current leads, voltage lags
Term
 phase shift in resistor
Definition
 V and I change together
Term
 Dissipate means?
Definition
 store E
Term
 Voltage can be describe by a change in ___
Definition
 current... no change in current = no V
Term
 Phase shift in inductors
Definition
Term
 In an inductor, reactance increases/decreases with a higher f
Definition
 increases
Term
 To increase frequency of resonance, you need to increase/decrease capacitance.
Definition
 decrease
Term
 When an AC circuit is being driven at it's resonant frequency, how do Vc and Vl compare?
Definition
 they are equal
Term
 A coil with I acts as a ____ and generates ___.
Definition
 motor, back torque
Term
 In transformers, increasing the current in the primary increases ___ through primary and secondary
Definition
 flux
Term
 electromagnetic fields involve an electric and a magnetic field that are parallel/perpendicular to each other
Definition
 perpendicular
Term
 ____ light "bounces" off a surface
Definition
 reflected
Term
 ___ light travels through the material
Definition
 transmitted
Term
 Which gives the largest average energy density at the distance specified? and what does this mean?a. 50W source at distance Rb. 100W source at distance 2Rc. 200W source at distance 4R
Definition
 a -- best illumination
Term
 ___ can generate E field or detect it, depending which direction the field is going
Definition
 dipole antennas
Term
 ___ antenna generates B field
Definition
 magnetic
Term
 Which is more important as far as intensity goes? R or P
Definition
 R
Term
 If the E field of an EM field is doubled, the energy density is ?
Definition
Term
 Absorption in an oscillating EM field is only achieved when?
Definition
 when there's resonance
Term
 When energy is absorbed, what direction is impulse?
Definition
 forward
Term
 ____ is the plane in which E field is aligned... provides net direction
Definition
 polarization
Term
 A polarizer does what to light?
Definition
 rotates it
Term
 A ray of light is transmitted through two polarizers that are perpendicular to each other. How much light gets through? If a third polarizer at 45deg to the first two is inserted between them, does any light get through? What does this prove? What would happen if we were to insert an optically active material instead?
Definition
 none, yes, cancelled light can reappear, more light would get through
Term
 Optically active materials that can rotate light are comparable to? What component of the materials determines how much they will rotate light?
Definition
 multiple polarizers, length
Term
 In solids that rotate polarization, very little __ is lost.
Definition
 Intensity
Term
 Polarization and reflection: Brewster's angle
Definition
 When the angle between the refracted ray and the reflected ray is 90deg, the reflected beam is 100% polarized
Term
 Sounds moves with respect to ___.
Definition
 air
Term
 ___ spectra are produced by thin gasses. Lines correspond to photons emitted when excited atomic states in the gas make transitions back to lower-lying levels.
Definition
 emission
Term
 ___ spectrum: solids, liquids or dense gases emit light at all wavelength when heated.
Definition
 Continuum
Term
 ___ spectrum occurs when light passes through a col, dilute gase. atoms in the gas absorb at characteristic frequencies. re-emitted light is unlikely to be emitted in the same direction --> dark lines in the spectrum.
Definition
 absorption
Term
 For the doppler effect for light, v is pos/neg if you are moving toward the object
Definition
 pos
Term
 If you aim a doppler radar at an object moving toward you, the return beam is blue/red shifted
Definition
 blue -- blue shift returns to a higher frequency, red shift returns to a lower frequency
Term
 Total internal reflection
Definition
 why a diamond looks so sparkly -- when theta=sin-1(n1/n2), theta2=90deg ... light is completely reflected so that more rays go directly back to observer
Term
 Prism effect on refraction
Definition
 double effect of refraction
Term
 The spreading of light into it's component colors is called
Definition
 dispersion
Term
 In a prism, which light gets deflected more? red or blue
Definition
 blue
Term
 Lens abberation
Definition
 when a thin lens blurs the image instead of focusing it
Term
 ___ occurs when rays far away from the principle axis do not focus at the same point as those rays close to the principle axis
Definition
 spherical abberation
Term
 ___ occurs when different wavelengths of light focus at different points because different colors experience different indices of refraction when passing through the lens
Definition
 chromatic abberation
Term
 Fixing chromatic abberation
Definition
 use different lenses with different indexes of refraction
Term
 Process by which the eye focuses by relaxing or contracting the lens
Definition
 accomodation
Term
 Total phase shift comes from both ___ effects and ____ effects
Definition
 surface and path
Term
 If you hold a small hand mirror close to you and then move it away, do you see more, less, or the same amount
Definition
 same
Term
 An ammeter measures ___, so if a wire is connected to an ammeter and surrounding a solenoid, and there is increasing current in the solenoid, what will the ammeter reading be?
Definition
 current, positive -- because increasing current = pos reading
Term
 The image created by a standard slide projector is real/virtual, smaller/larger
Definition
 real, larger
Term
 The image created by a camera is real/inverted, smaller/larger
Definition
 real, smaller
Term
 The image created by a magnifying glass is real/inverted, smaller/larger
Definition
 inverted, larger
Term
 When light is reflected from the interface between two transparent surfaces, its phase shifts by 180 degrees only when?
Definition
 when the material on the incident side has a smaller n than that on the other side
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