Physics Controlled Assessment/ISA?
We are doing a controlled assessment in physics about how Light Dependent Resistors are affected by light intensity.
My hypothesis is:
'The higher the light intensity, the lower the resistance of a light dependent resistor'
I am aware that on paper 1, there may be a question where it asks WHY I chose the hypothesis. I don't know what to write other than 'This is because as the light intensity increases, the resistance of the LDR decreases' which is basically the same as my hypothesis.
Can anyone help and suggest what I could write for that question? Also are there any tips on how to do well on it?
Thank you.
My hypothesis is:
'The higher the light intensity, the lower the resistance of a light dependent resistor'
I am aware that on paper 1, there may be a question where it asks WHY I chose the hypothesis. I don't know what to write other than 'This is because as the light intensity increases, the resistance of the LDR decreases' which is basically the same as my hypothesis.
Can anyone help and suggest what I could write for that question? Also are there any tips on how to do well on it?
Thank you.
Scroll to see replies
@longshot100 I remember you gave an explanation in another one of these threads. Mind helping this clueless GCSE student?
Spoiler
You don't need to do prep for the ISAs. The most wingable exams out of all of the ones you'll ever take 
It's because LDRs are made of semiconductors- unlike normal conductors, they conduct better under higher heat/light.
This means the resistance is decreasing.
As to why-
Semiconductors' electrons will become 'excited' (yep, thats what its called) as it gains more energy from light or heat, and this frees up more electrons to carry charges across the semi conductor.
The more electrons there are, the less resistance the semi conductor has.
The LDR behaves like this because it uses a semiconductor which gets its electrons excited through light energy
This means the resistance is decreasing.
As to why-
Semiconductors' electrons will become 'excited' (yep, thats what its called) as it gains more energy from light or heat, and this frees up more electrons to carry charges across the semi conductor.
The more electrons there are, the less resistance the semi conductor has.
The LDR behaves like this because it uses a semiconductor which gets its electrons excited through light energy
The points you'd need to include is the LDR being a semi conductor
The semi-conductor in LDRs will reduce resistance due to the energy gained from light (Heat if thermistors)
The energy lets some electrons move around freely (same as the free electrons in metals which allow them to conduct).
so MORE LIGHT ENERGY=MORE FREED ELECTRONS=BETTER CONDUCTOR=DECREASED RESISTANCE
I don't know if this makes anymore sense for you, but I hope the last bit will help you.
The semi-conductor in LDRs will reduce resistance due to the energy gained from light (Heat if thermistors)
The energy lets some electrons move around freely (same as the free electrons in metals which allow them to conduct).
so MORE LIGHT ENERGY=MORE FREED ELECTRONS=BETTER CONDUCTOR=DECREASED RESISTANCE
I don't know if this makes anymore sense for you, but I hope the last bit will help you.
Original post by longshot100
No problem!
Looks like someone's been keeping an eye on me...
Looks like someone's been keeping an eye on me...
Spoiler
Sure, we'll go with that
Spoiler
Original post by longshot100
The points you'd need to include is the LDR being a semi conductor
The semi-conductor in LDRs will reduce resistance due to the energy gained from light (Heat if thermistors)
The energy lets some electrons move around freely (same as the free electrons in metals which allow them to conduct).
so MORE LIGHT ENERGY=MORE FREED ELECTRONS=BETTER CONDUCTOR=DECREASED RESISTANCE
I don't know if this makes anymore sense for you, but I hope the last bit will help you.
The semi-conductor in LDRs will reduce resistance due to the energy gained from light (Heat if thermistors)
The energy lets some electrons move around freely (same as the free electrons in metals which allow them to conduct).
so MORE LIGHT ENERGY=MORE FREED ELECTRONS=BETTER CONDUCTOR=DECREASED RESISTANCE
I don't know if this makes anymore sense for you, but I hope the last bit will help you.
Thank you so much for posting this!
Original post by CookieMonster456
Thank you so much for posting this!
No problem!!!
Original post by longshot100
Ahh, a fellow GCSE student! Is yours also on LDRs? Idk why everyone wants to know about the LDR one now, we did ours at the beginning of this school year...
You're so lucky that you did yours at the beginning of the school year, our school loves leaving things to the last minute :/ they're making us do it all in one day!
Original post by longshot100
Ahh, a fellow GCSE student! Is yours also on LDRs? Idk why everyone wants to know about the LDR one now, we did ours at the beginning of this school year...
No. I like to research on all the ISA practicals for fun.
Spoiler
Original post by TheOtherSide.
No. I like to research on all the ISA practicals for fun.Eh, we focused on Biology and Chemistry at the beginning of the school year, so we're left with Physics now. Do you guys still have coursework in other subjects left?
Spoiler
I have my physics ISA, a Spanish writing, textiles coursework and music coursework, although my music teacher seems to have other priorities than marking my work so I don't know how that's going at the moment :s
Original post by longshot100
Well, we just need to do paper 2 for Chemistry then we're done with ISAs.
I've got my Astronomy coursework due in for March, but the weather has been **** recently, so I couldn't do observations of the moon (cutting it close, I know)
We've also got some French Speaking and English (Language? Maybe.) coursework starting next week.
I've got my Astronomy coursework due in for March, but the weather has been **** recently, so I couldn't do observations of the moon (cutting it close, I know)
We've also got some French Speaking and English (Language? Maybe.) coursework starting next week.
Lucky... my last piece of coursework needs to be handed in on the last week of this term (before Easter Holidays) so we've got fewer lessons to focus on revision. Don't know how I'll cope
Original post by TheOtherSide.
Lucky... my last piece of coursework needs to be handed in on the last week of this term (before Easter Holidays) so we've got fewer lessons to focus on revision. Don't know how I'll cope
Do a ton of revision at home (well, maybe not a ton, but enough)
Original post by longshot100
Do a ton of revision at home (well, maybe not a ton, but enough)
Easier said than done...
Original post by TheOtherSide.
Easier said than done...
Have you guys started revising yet?
Original post by CookieMonster456
Have you guys started revising yet?
Nope
Original post by longshot100
My timetable is pretty rough and adaptable, but it helps.
When I get home, I faff about and watch TV etc for an hour. Then I revise for a few hours then do what I want/need to do.
When I get home, I faff about and watch TV etc for an hour. Then I revise for a few hours then do what I want/need to do.
I sort of made a timetable before mocks, but I ended up not using it - being organised just does not work for me.
Original post by longshot100
Keep a textbook of your worst subject with you and read our whenever you feel guilty... Even on the toilet seat.
Since my worst subject is probably English, there isn't much I can do, apart from rereading the texts (okay, I suppose I could do that...)
What would you say is your worst subject?
Original post by longshot100
I'm good at most subjects (2A*s, rest As), but the two weakest subjects were Art(because you need to be crazy good at it) and History (bad teacher for GCSE years (he's gone now)). I didn't get As in those... But I passed.
Yep, so glad I didn't take art
Oh yeah, History... the essay question at the end completely mucked up my grade
It's pretty clear that I'm not an English-y person at all.Original post by longshot100
How did you fare in the mocks?
Mainly apart from History, alright, I suppose - especially considering I'll do much more revision for the real thing (I hope so!)
Spoiler
Guessing yours went better?
(edited 8 years ago)
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