HSC Physics - 2014 Predictions (3 Viewers)

[Fade1233]

Lol some of this may help although a lot of it may be out of syllabus (disclaimer, there may be a few typos which I haven't fixed up yet in there).

http://community.boredofstudies.org/265/ideas-implementation/323842/transistor.html

Now you just need to know how diode works. I dont think you need to know how transistors work but only its impacts on society.

 

[screwuhsc]

Can someone explain to me What a photocell is and how it works thanks kind a confused

 

[Fade1233]

Can someone explain to me What a photocell is and how it works thanks kind a confused

Continuous large voltage between electrodes-> incident light of threshold freq -> Emission (photoelectric effect)-> voltage accelerates electrons (which would otherwise not accelerate due to air being excellent insulator) -> circuit closed-> Signal.

 

[Rhinoz8142]

Can someone explain to me What a photocell is and how it works thanks kind a confused

The photocell work by the photoelectric effect, which electromagnetic radiation is exposed to metal result to the emission to electrons. In a photocell it contain a n types semiconductor. So when sunlight is emittied onto the photocells the electrons are emitted which is then collected by the cathode. But this only happens when the electromagnetic radiation frequency's is more than the threshold frequency of the metal (i think)

 

[mreditor16]

The photocell work by the photoelectric effect, which electromagnetic radiation is exposed to metal result to the emission to electrons. In a photocell it contain a n types semiconductor. So when sunlight is emittied onto the photocells the electrons are emitted which is then collected by the cathode. But this only happens when the electromagnetic radiation frequency's is more than the threshold frequency of the metal (i think)

you're confusing the photocell with a solarcell.

 

[Rhinoz8142]

you're confusing the photocell with a solarcell.

whats the difference

 

[QZP]

whats the difference

a solarcell is a specialised photocell. a photocell in general doesn't involve semiconductors

 

[Rhinoz8142]

a solarcell is a specialised photocell. a photocell itself doesn't involve semiconductors

So how dose a "photocell" work then

 

[QZP]

open the textbook

 

[screwuhsc]

ahaha cheer guys

 

[screwuhsc]

whats one advantage of having magnetic levitation?

 

[seventhroot]

whats one advantage of having magnetic levitation?

there requires no contact between the surfaces. you can use it in something like brakes so they reduce wear and tear

 

[screwuhsc]

can u also say therefore its suitable for trains for that reason (frictionless surface) which give them high speeds?

 

[seventhroot]

can u also say therefore its suitable for trains for that reason (frictionless surface) which give them high speeds?

having magnetic levitation doesn't directly mean you will have 'higher speeds'. MagLev trains are more complicated than that but yes using magnetic levitation in these special trains would also be another good example

 

[screwuhsc]

is this a good answer for discussing the BCS theory
Atoms in a crystal lattice constantly vibrate. This is because they are
all connected and these vibrating atoms create waves throughout the
metal called phonons. The more the atoms are vibrating
the larger the phonons. In superconductors (at
low temperatures) the phonons are small, and any distortion caused
by the electrons is reflected in phonons. These phonons can attract
electrons to form cooper pairs
According to the Barden-Cooper-Schrieffer theory, atoms of metals in
the superconducting state will have electrons that lock and travel
together throughout the lattice. This pair of electrons causes the
lattice to distort as the electrons move unimpeded.
This is because their strong negative charge will repel any positive
atoms that it gets close to, thus no collisions occur and electron flow is not resisted.

 

[screwuhsc]

As explained by the BSC theory, when a superconductor is cooled below its critical temperature
electrons begin to pair known as a cooper pair. A → Cooper pair consists of two
electrons that are a considerable distance apart. The attractive
force between the two electrons is provided by the exchange of
phonons (lattice vibrations).

 

[seventhroot]

is this a good answer for discussing the BCS theory
Atoms in a crystal lattice constantly vibrate. This is because they are
all connected and these vibrating atoms create waves throughout the
metal called phonons. The more the atoms are vibrating
the larger the phonons. In superconductors (at
low temperatures) the phonons are small, and any distortion caused
by the electrons is reflected in phonons. These phonons can attract
electrons to form cooper pairs
According to the Barden-Cooper-Schrieffer theory, atoms of metals in
the superconducting state will have electrons that lock and travel
together throughout the lattice. This pair of electrons causes the
lattice to distort as the electrons move unimpeded.
This is because their strong negative charge will repel any positive

feed back:
- write BCS; don't need to waste your time
- fairly unclear
- not really accurate

out of 5 maybe 2 or 3 being generous

 

[screwuhsc]

what including the 2nd part?

 

[screwuhsc]

i didnt finish that answer lol

 

[seventhroot]

i didnt finish that answer lol

make another post with your final answer