Qualification > Sciences
Help!!
Deadly_king:
--- Quote from: cs on September 08, 2010, 01:33:35 pm ---@Deadly_king
Thank you so much, i really appreciate it. I got the calculation for Nov 03, No 34 correct! i am so poor at that.. +rep!!
I am preparing for my AS this OCT and its school holiday in my country here, couldn't believe that you solved the questions so fast.
--- End quote ---
Its ok dear..........am actually sitting for A2 this october. so am bound to be more prepared than you :P
Try to practice more papers......am sure you'll perform well then!
Deadly_king:
--- Quote from: cs on September 08, 2010, 01:47:07 pm ---I have another question, Nov 2005 Q 37 (the "light level" part)
--- End quote ---
As light intensity increases the resistance of the LED decreases.
This is the only thing you need to remember about LED. Just memorize that and you'll be able to do every question about it :)
Since resistance of LED decreases the voltage across it will increase as voltage is inversely proportional to its resistance.
I believe you understood the temperature part.
Answer is C
cs:
But deadly_king, why is the answer low light level..? as you said the voltage increase, when resistance decrease- where the light intensity increase.. shouldn't it be high light level..? its there something wrong with my english that i misunderstood the answer?
cs:
Sorry to bother anyone, but i cannot get the answer for June 2006 33,34 and 37. Any help will be greatly appreciated..
Deadly_king:
--- Quote from: cs on September 08, 2010, 02:52:55 pm ---But deadly_king, why is the answer low light level..? as you said the voltage increase, when resistance decrease- where the light intensity increase.. shouldn't it be high light level..? its there something wrong with my english that i misunderstood the answer?
--- End quote ---
Actually i made a small mistake. I apologise for that. seems you understood well :)
V = IR.........Voltage is directly proportional to resistance.
let me clear your mind.
The questions ask when both readings on VT and VL are high.
When VL is high.........the resistance of the LED should be high. For the resistance to be high the light intensity should be low.
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