# OCR Physics A Exam - G482 Electrons, Waves, Photons [09/06/16]Watch

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3 years ago
#61
(Original post by Tyler'sD)
Good paper for me, the ones im not sure if i got was the why the 3ohm resistor and i dont know if i proved it was 30mA correctly in the LED, i worked out the LED resistance then worked out the voltage in the resistor then worked out the current, it that what everyone else did??
I found p.d. across the LED, resistance from graph at 30mA, then subbed into v=IR, showing current is 30mA.. got resistance to be 100 ohms
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3 years ago
#62
Generally I thought the paper was ok. Stationary wave one I thought was alright but that first question with A1 and A2. I had no idea on! Wasn't sure what was going on. Didnt like the fuse one either because I couldn't tel what was in series and what was in parallel with the 8. A few bits here and there were rank too but generally ok.
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3 years ago
#63
(Original post by RBoss)
I found p.d. across the LED, resistance from graph at 30mA, then subbed into v=IR, showing current is 30mA.. got resistance to be 100 ohms
Thats what i did
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3 years ago
#64
(Original post by RBoss)
I found p.d. across the LED, resistance from graph at 30mA, then subbed into v=IR, showing current is 30mA.. got resistance to be 100 ohms
yeah i got 100 too
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3 years ago
#65
(Original post by Hasib98)
Thats what i did
Yeh same.
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3 years ago
#66
What did everyone put for the fuse question? I put 50mA because I worked out the total current of the circuit to be like 15mA. Seems way too low though....
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3 years ago
#67
Did anyone get the current to be 89/90 mA, so fuse value was 500mA?
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3 years ago
#68
(Original post by RBoss)
Did anyone get the current to be 89/90 mA, so fuse value was 500mA?
I said the fuse value was 50mA because my current was around 30mA.
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3 years ago
#69
(Original post by NickLCFC)
What did everyone put for the fuse question? I put 50mA because I worked out the total current of the circuit to be like 15mA. Seems way too low though....
I have no idea if I got it right but I got the current to be about 20 mA so also put 50mA
1
3 years ago
#70
Definitely think it was fine, though unusual. I know I messed up the harmonics hard, thankfully that wasn't toooo many marks, and I am very confident I got at least a part of it right... (the speed part). I think most of it wasn't too hard, reckon I did well, an A or a B I think. Definitely much better than last year is any case.
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3 years ago
#71
(Original post by NickLCFC)
What did everyone put for the fuse question? I put 50mA because I worked out the total current of the circuit to be like 15mA. Seems way too low though....
From what I remember, the resistances of LED and resistor in series was 167 ohms, so total resistance was 55.6..., so I = V/R = 5/55.666 = 90mA
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3 years ago
#72
(Original post by RBoss)
From what I remember, the resistances of LED and resistor in series was 167 ohms, so total resistance was 55.6..., so I = V/R = 5/55.666 = 90mA
Didn't they arrange the 100ohms LEDs and 67ohms resistors in parallel though? From what I can remember, there was 7 parallel 'arms' of a resistor and LED in series
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3 years ago
#73
(Original post by Tyler'sD)
yeah i got 100 too
For the eV = 1/2 mv^2 question, I did eV = h / mv instead, do you think I will get any kind of marks?
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3 years ago
#74
(Original post by NickLCFC)
Didn't they arrange the 100ohms LEDs and 67ohms resistors in parallel though? From what I can remember, there was 7 parallel 'arms' of a resistor and LED in series
Snap yeah there would have been 7 LED's in parallel, with one resistor, and then 3 lots of the total resistance in parallel to make the 3 digit display
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3 years ago
#75
Resistance was 67/3 and V was given as 5 so do I=v/r and i was ~220mA therefore i selected 500mA anyone else do this?
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3 years ago
#76
(Original post by Abb97)
Resistance was 67/3 and V was given as 5 so do I=v/r and i was ~220mA therefore i selected 500mA anyone else do this?
I think you're right. I've just had another go at it from how I can remember the question and got the same answer as you
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3 years ago
#77
Did anyone get 340ms-1 for the wave speed? And what was the fundamental frequency was that just 512hz i didnt know what to do for that 1 mark??
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3 years ago
#78
Yh i looked at that question carefully pretty sure its right
(Original post by NickLCFC)
I think you're right. I've just had another go at it from how I can remember the question and got the same answer as you
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3 years ago
#79
(Original post by Abb97)
Did anyone get 340ms-1 for the wave speed? And what was the fundamental frequency was that just 512hz i didnt know what to do for that 1 mark??
Yeah I got something like 340, and I got 256Hz for the fundamental frequency (512/2)
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3 years ago
#80
(Original post by Abb97)
Did anyone get 340ms-1 for the wave speed? And what was the fundamental frequency was that just 512hz i didnt know what to do for that 1 mark??
Fundamental frequency would have been 3 * 512 I think.
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