Need help on afew questions (1 Viewer)

[someth1ng]

I have some that I need to do (20 questions) but I can't do all of them. I need help with the following:

1. Explain why the potential difference across the device does not vary once the potential difference across it has reached 0.7 volts, even though there is a significant increase in current through this device in this range. [This is the context of semiconductors and refers to a "current vs potential difference" graph where it rises exponentially at ~.55V and at 0.7V it is almost vertical]
2. Explain how Hertz's demonstration supported Planck's development of black body theory.
3. "Science progresses in a social context, but can als change the direction of the society, and the lives of Scientist." Discuss with reference to Edison and Westinghouse. [I don't need an answer but a proper explaination to what it is asking - is it asking about the conflict between Edison and Westinghouse and why Westinghouse won?]
4. A mass spectrometer is widely used in chemical analysis to separate ions of different mass (m) and charge (q). Atoms ionised by a hot filament are accelerated in an electric field to a velocity of v ms-1 before they enter a uniform magnetic filed (B). In the magnetic field they experience a centripetal force that results in their circular path of radius r metres. Identify the important principles of physics that you studied in the Ideas to Implementation topic that have resulted in our understanding of matter as particles.

Thanks in advance
-someth1ng

 

[Fizzy_Cyst]

Are you already up to I2I?

1. This 0.7V is specifically referring to a silicon diode. It is to do with the fact that when you sandwich P and N-type SC together to form a PN junction, some of the charge carriers migrate across the SC and build up an electric field in sucha direction that electrons can not migrate across the electric field) -- When 0.7V isapplied across the PN junction (forward biased) it effectively negates the elecgtric field due to the migration of the charges and allows electrons (and holes) again to move through the depletion region.

The others will take a while to answer, so I will be back

2. I would talk about how Maxwell predicted with his equations of electromagnetism that there was a whole spectrum of EM waves, rather than just the observed visible and IR rays. Then, how Hertz set out to prove this by using a rapidly oscillating electric field with an induction coil. He then discovered EM waves of different wavelengths. Then tie this in to the idea of how black bodies release an entire spectrum of EM waves.

3. The question is basically saying how can science change society? I.e., before AC everything was run on DC, Edison had heaps of DC power stations and all his devices ran on DC, then when AC came everything changed. Kind of like everything used to be recorded on tape, then the CD came along and make it obsolete. Same kind of thing.

 

[someth1ng]

Are you already up to I2I?

We're doing Space and Astrophysics last - my school has a rather strange order for Physics: Motors and Generators --> Ideas to Implementation --> Space --> Astrophysics
I'm also a few PFAs faster since I like to learn ahead of my class.

This 0.7V is specifically referring to a silicon diode. It is to do with the fact that when you sandwich P and N-type SC together to form a PN junction, some of the charge carriers migrate across the SC and build up an electric field in sucha direction that electrons can not migrate across the electric field) -- When 0.7V isapplied across the PN junction (forward biased) it effectively negates the elecgtric field due to the migration of the charges and allows electrons (and holes) again to move through the depletion region.

This is really complicated...are you saying that in this case: when you stick a p SC and an n SC together, the "extra eletrons" in the n SC migrate towards the p side to fill in the "holes" until there's an equilibrium. When you connect the diode in a "forward bias" (negative to n-type, positive to p-type) way, there is a resistance since one side of the diode is negative and one is positive so when potential difference is increased, it creates a "balance" again where there is no more charge imbalance?

Or...n-doped side of the diode is connected to the negative side --> then negates the electric field and current flows?

Q4 is the one I'm finding most trouble with understanding what the question is asking - it doesn't seem very well worded in my opinion.

 

[someth1ng]

I would talk about how Maxwell predicted with his equations of electromagnetism that there was a whole spectrum of EM waves, rather than just the observed visible and IR rays. Then, how Hertz set out to prove this by using a rapidly oscillating electric field with an induction coil. He then discovered EM waves of different wavelengths. Then tie this in to the idea of how black bodies release an entire spectrum of EM waves.

But I don't see how this shows it's relation to Planck's Black Body theory.

 

[IamBread]

But I don't see how this shows it's relation to Planck's Black Body theory.

I think they're talking about cathode rays and how we came to the conclusion that they were particles, not waves.

 

[someth1ng]

I think they're talking about cathode rays and how we came to the conclusion that they were particles, not waves.

It's either that experiment or the radio waves one - I'm not sure how either are really related though. I just can't see it!

 

[IamBread]

It's either that experiment or the radio waves one - I'm not sure how either are really related though. I just can't see it!

Oh sorry that was the wrong quote lol. I was talking about Q4

 

[someth1ng]

Just out of pure curiosity, for those super conducting metal alloy oxides, at room temperature, would they still be conductors?