General Thoughts: Physics (4 Viewers)

[panda15]

Lol. Would their be a mark for saying. "The photoelectric effect is the basis for its operation. The photoelectric effect is..."?
Btw would the diagram be 1 or 2 of the 5 marks?

I'd say the diagram would be worth 2.

 

[anomalousdecay]

So according to physics in focus... they are used to activate alarms and automatic doors. Is this correct? Just hoping I can get 1/5 considering I wrote all the lines. Didn't do a diagram though...

I actually wrote on mine that it uses any type of EMR and one example as is used in burglar alarms for the solar cell set-up.
I am may be wrong because I am not sure whether electrons can be knocked out of the depletion layer simply by infra-red. I did write about threshold frequency but then again you need a complex semiconductor that can still work for infra-red.

 

[Menomaths]

I actually wrote on mine that it uses any type of EMR and one example as is used in burglar alarms for the solar cell set-up.
I am may be wrong because I am not sure whether electrons can be knocked out of the depletion layer simply by infra-red. I did write about threshold frequency but then again you need a complex semiconductor that can still work for infra-red.

That's not how they work. When there's a lack of incident ray (when the burger crosses the emitter) an alarm goes off due to the lack of the elections being emitted. (overly simplified)


My English is probably peaking because I'm tired af atm so excuse the B6 English

 

[anomalousdecay]

That's not how they work. When there's a lack of incident ray (when the burger crosses the emitter) an alarm goes off due to the lack of the elections being emitted. (overly simplified)


My English is probably peaking because I'm tired af atm so excuse the B6 English

I always thought it was the opposite. Does the human body release infra-red or does it absorb?

 

[Menomaths]

I always thought it was the opposite. Does the human body release infra-red or does it absorb?

Releases, what do you mean opposite? Theres an emitter and an reciver, I'll show a diagram:

O-----------------------------------------------)
^Emitter............................................Receiver^
Everything's all good.
Now put a burger there

O---------- (]|||] -------------------------------)

Since the ray can't hit the receiver, an alarm goes off

 

[anomalousdecay]

Not the ones I have in my house.
Ours is just infra-red and when someone walks past it goes off.

 

[anomalousdecay]

Ours is more of an LDR, but is most likely just infra-red instead.

 

[Menomaths]

Not the ones I have in my house.
Ours is just infra-red and when someone walks past it goes off.

Obviously there can be different types of alarms that work on different principles.

 

[anomalousdecay]

Obviously there can be different types of alarms that work on different principles.

True. I guess I'll be more happy when I'm doing electrical.

 

[anomalousdecay]

I really, really, really hope that the markers for my paper have done Age of Silicon, cause they will know what point I tried to make.

 

[Menomaths]

I really, really, really hope that the markers for my paper have done Age of Silicon, cause they will know what point I tried to make.

Hopefully

 

[anomalousdecay]

Hopefully

So anxious for results. Our school is very volatile on yearly results.
One year highest 92. Next year 78.
Hopefully three 90's this year.

 

[Menomaths]

So anxious for results. Our school is very volatile on yearly results.
One year highest 92. Next year 78.
Hopefully three 90's this year.

I don't even care lol

 

[MATHmaster]

Unless she is in the group of teachers who come up with the marking scheme for the question, her 'confirmation' means diddly squat!

In terms of the syllabus, photocells and solar cells are two COMPLETELY different dot points, in two COMPLETELY different sections.

Whenever the word photocell or photoelectric cell has been used in HSC previously, it has been referring to the anode / cathode arrangement. A solar cell has never been referred to as a photocell previously.

I can see the arguments for either side, but i would put my money on them saying anode / cathode arrangement is a photocell. I suppose we need to wait til the marking guidelines are released!

Well she had a look at the paper months before it was released, and thus knew the marking guidelines beforehand. I called her and she said solar cells are fine to use and I won't get penalised for it

 

[Menomaths]

Well she had a look at the paper months before it was released, and thus knew the marking guidelines beforehand. I called her and she said solar cells are fine to use and I won't get penalised for it

What? Is that why JR is coming #1 all the time?

 

[MATHmaster]

What? Is that why JR is coming #1 all the time?

LOL

 

[nerdasdasd]

Looks like you guys had to do a decent paper (y)

 

[Randox]

Looks like you guys had to do a decent paper (y)

What do you estimate b5 an 6 cut off?

 

[uart]

This is what the Jacaranda textbook says about photocells, why are solar cells wrong to mention?

A photocell is a device that uses the photoelectric effect. These devices include photovoltaic, or solar cells, which convert electromagnetic energy, such as sunlight, into electrical energy. Other examples are photoconductive cells and phototubes.

pg 207

Someone explain why drawing a solar cell is wrong?

You make a really good point. I hate the use of the term photocell to describe a light dependent resistor.

The technically correct term for a solar cell is a “photovoltaic cell” and the best term for a light dependent resistor is (in my opinion) “a light dependent resistor” or a "photoresistor", not a “photocell”. (I always prefer a more descriptive name over one less so).

Also the word “cell” usually carries a connotation of a source of electrical power when used in an electrical context, which is another reason not to like the term “photocell” to describe a light dependent resistor. Having said that however, people do often use the term photocell to refer to a light dependent resistor, so I think that was indeed what you were expected to describe here. Sorry

The use of the term photocell to describe what many would more commonly know as a light dependent resistor, and could easily confuse with a photovoltaic cell, is a total act of bastardy by the BOS. Particularly to have a whole 5 mark question hanging on just the meaning of this one word, with absolutely no other clues or context to guide you. I mean how fricking hard would it have been for them to word the questions as:

With the aid of a diagram explain how a photocell (light dependant resistor) works.

Grrrrrrrrrr.

 

[uart]

I got 51.91 but not sure why g is 9.8. Is the space station being tested on earth

No, but it's simulating the gravity of Earth, hence we use the same value.

BTW. Sorry I haven't read all the replies here but from what I've read it looks like no one has put this answer into units of *rotational* speed (eg radians per second, revs per second, revs per minute etc).

The correct linear speed at the circumference is 51.91 m/s, but shouldn't you divide this by (2 pi r) and give the results in revolutions per second or similar units? Or is circumferential speed considered a good enough answer for "rotational speed".