• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/42

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

42 Cards in this Set

  • Front
  • Back
three experiments that gave birth to Quantum mechanics
1. Blackbody Radiation
2. Photoelectric Effect
3. Compton Effect
Particles of zero rest mass
photons
Small particles of matter act like...
both waves and particles. observing this though can affect how it behaves.
Heisenberg uncertainty principle
Particles position and momentum cannot be measured simultaneously.
Outcome of the Michelson – Morley experiment
the speed of light is independent of observers speed
Postulates of Special theory of relativity
1. The laws of physics are the same in all inertial reference frames.
2. The speed of light is constant with respect to all observers regardless of their speed.
Time dilation
moving clocks run slowly
Length contraction
moving meter sticks are shortened
space-time
4th dimension- 3 space+1 time
generator
provides electric power, requires mechanical power

Consists of a loop of wire mounted on a rod that can rotate. The loop is attached to a power source and placed between the poles of a magnet.
motor
provides mechanical power, requires electrical power

An outside force moves magnets in a circle past several coils of wire.
transformer
a device that increases or decreases the voltage of alternating current

Operates on the principle that a current in one coil induces a current in another coil.

One coil is called the primary coil and the other is called the secondary coil.
AC passing through the primary coil creates a magnetic field.
Electromagnetic induction causes a current to flow in the secondary coil.
A transformer can change the voltage and current while keeping power unchanged
household power is...
ac (alternating current)
step down transformer
fewer loops in the secondary coil than in the primary coil, therefore the voltage of the secondary coil is less than the primary coil.
Used to lower the voltage to 120 volts before it can be used in homes and offices
step up transformer
more loops in the secondary coil than in the primary coil, making the voltage of the secondary coil greater

Used by power companies to transmit high-voltage electricity.
three-phase transformers
constructed by winding three single-phase transformers on a single core
circuits are made up of...
a source of electricity (such as a battery), a load (a light or motor) and two wires to carry electricity between the two. Electrons move from the source, through the load, and back to the source.
These moving electrons have what we call energy. As they move they can do work.
increasing either the current (i) or the voltage (V)
will increase power output (P).
Increase resistance in the wires
voltage drops, current drops > power output drops.
battery
is a simple electrical circuit and source

When you load a battery into an electronic device, the negatively charged electrons will travel to the portion of the battery with a positive charge - much like water flowing down a stream and being forced to turn a water wheel.
DC
direct current

Batteries (and solar cells) produce DC. The positive and negative terminals of a battery are always positive and negative. Current always flows in the same direction between the two terminals.
power substation for power plant
transformers bring down the voltage to distribution voltages.
a busbar splits the distribution power off in multiple directions.
circuit breakers and switches to allow the substation to be disconnected from the transmission grid or separate distribution lines.
To read the magnetic strip on an ID or credit card, you must swipe it quickly past a tiny coil of wire. Why must the card be moving for the coil system to read it?
A changing magnetic field will induce a voltage in the wire, causing a current. If the card is moving past the reader, the coil will experience a changing magnetic field as the magnetized pieces of the strip pass by, and this will cause a current in the wire. If the card is not moving, the field will be static, and no current will be induced!
If you plug too many appliances into a socket that has nothing to limit the current it can supply, the outlet and home wiring will become hot. Why?
A low resistance in the circuit will result in a very large current, according to Ohm’s Law. This will result in a large amount of power supplied by the battery, since Power = Current * Voltage. All this power must be used up by the circuit, and this power will result in the generation of a lot of thermal energy, heating the wires.
A fuse contains a short wire with a relatively high electric resistance. Why will this wire melt first if too much current is drawn through the circuit?
Since the wire has a relatively high resistance, the drop in voltage across the wire will be relatively high, according to Ohm’s Law (V = IR). Since the power lost in a circuit element is equal to the current * the voltage drop (P = IV), the power lost in the fuse will be higher than in the rest of the wire. This power results in the generation of lots of thermal energy, heating the wire and causing it to melt.
Iron and steel scraps in the trash are attracted to the poles of the electromagnet but aluminum scraps are not. Why do these metals behave so differently?
The aluminum is a non-magnetic metal, so it is not magnetized by the electromagnet.
If they're moving fast enough, aluminum scraps experience a magnetic drag force that separates them from nonmetallic trash. What is the origin of this force?
The aluminum scraps experience a changing magnetic field as they pass by the electromagnet. This induces a current in the aluminum scraps, which, in turn, produces another magnetic field. The induced magnetic field always opposes the field which created it, so it will slow the aluminum down.
To look for metal hidden inside bundles of paper, the recycling plant exposes the bundles to an alternating magnetic field (one that reverses directions many times a second). If it finds that something inside a bundle creates another alternating magnetic field in response, it knows that the bundle contains metal. How can metal inside the trash create this second alternating magnetic field?
An alternating magnetic field changes in time, and so any metal inside the bundle will experience a magnetic field. This will induce an alternating voltage in the metal, which will result in an alternating current in the metal, which will in turn produce an alternating magnetic field. (This is how a metal detector works!)
When astronauts walked on the surface of the moon, they could see the stars even though the sun was overhead. Why can’t we see the stars while the sun is overhead?
The atoms in the atmosphere scatter light from the sun, giving the sky a bright blue glow. The brightness of the stars is overcome by this glow, and we cannot see them during the day. But in moon there is no atmosphere. So no particles to scatter the light. Therefore the sky looks dark and astronauts could see the stars even in the day time.
To make a beams at a laser light show visible, they’re often directed into mist or smoke. Why are such particles necessary to make the laser beam visible?
Normally, the light in a laser beam would travel along the length of the beam and never reach our eyes, so we wouldn’t see it. However, if there is something in the path of the beam which scatters light towards our eyes, we can see this scattered light and know where the beam is. Particles of mist or smoke scatter light well, making the beam visible.
Diamond has an index of refraction of 2.42. If you put a diamond in water, you see reflections from its surfaces. But if you put it in a liquid with an index of refraction of 2.42, the diamond is invisible. Why is it invisible, and how is this effect useful to a jeweler or gemologist?
When light crosses the boundary between materials with different indices of refraction, it bends. This bending of light is what allows us to see objects even when they are clear. If a material is in a fluid which has the same index of refraction as the material, there will be no bending of light across the boundary, and so light will pass through as if the object were not there. This makes the object appear invisible.
A gemologist could use this to verify that a diamond is real – if a diamond disappears in a liquid with an index of refraction of 2.42, then it must also have an index of refraction of 2.42, indicating that it is, in fact, a diamond.
If you’re wearing polarized sunglasses and want to see who else is wearing polarized sunglasses, all you have to do is turn your head sideways and look to see which people now have sunglasses that appear completely opaque. Why does this test work?
A pair of polarized sunglasses, worn properly, will block all but vertically-polarized light. If you wear a pair of sunglasses sideways, then, they will block all but horizontally-polarized light. Your sideways pair of glasses will block all of the vertically-polarized light which passes through a stranger’s glasses, causing them to appear dark. (i.e. crossed polarizers block all light)
When white fabric ages it begins to absorb blue light. Why does this give the fabric a yellow appearance?
Removing the blue from the reflected light (by adsorbing it) leaves a disproportionate amount of red and yellow light (everything but blue, really) in the reflected spectrum, causing it to appear yellowish.
light
consists of varying magnetic and electric fields
primary colors of light
red, blue, green
refraction
The bending of light as it passes from one medium to another
dispersion
different colours of light have different wavelengths, this means they are bent (refracted) by different amounts
red-refracted the least(longest wave length), purple-refracted most(shortest wave length)
polarized light vs unpolarized light
Polarized Light
has E field in a
certain direction
vs

Un-polarized Light
has E field at any instant
can have E in any direction.
polarization by absorption
Some crystalline materials absorb more light in one incident plane than another, so that transmitted light is polarized.
crossed polarizers
No light is transmitted when two ideal polarizers (e.g., polaroid sheets) are ‘crossed’ (placed at right angles)
scattering
the redirection of radiation out of the original direction of propagation, usually due to interactions with molecules and particles
What will happen to the temperature of the room if you open the door to the refrigerator and let it run for a few hours?
If the refrigerator is let open for long time, hot air from room will get into the refrigerator and cool air will be pumped out from refrigerator. When the refrigerator cools the hot air, evaporator removes the heat from it and pump again to the room through working fluid. The condenser removes the heat from working fluid and pumps it to the room again. Eventually the refrigerator takes heat from room air and pump heat again to room air. The air near the refrigerator would become colder while the air in the room becomes hotter. Since the refrigerator will deliver more heat to the room air than tit absorbs from room air, on an average the room become warmer. In this way Second law of Thermodynamics also not violated. That is to say the entropy always increases.