AQA AS Level Electronics Unit 1 (ELEC1) 14 May 2013

It was actually a nice paper! Feeling pretty confident about it. Not sure about unit 2 though... The question about making an EXOR gate with NOT/AND/OR gates threw me a little bit but I got there in the end!

Reply 2

I was wondering If we get ecf ? I never see it on mark schemes. As for the paper it was pretty normal for me, they threw in a few extra tricks this time and some more describe and explain questions. Reckon grade boundaries will be as low as last year ?

Reply 3

By the way where do you two do electronics ? I saw there were only a few centers by looking at the teacher support group on ikes.

Reply 4

My teacher has always said that we get ECF. I'm guessing that the grade boundaries will be similar to last year, most of the students in my class found it similar difficulty to last years paper.

Reply 5

Ah cheers thats encouraging. For the question with the L.E.Ds and the 'long wires' in the theater did you need to mention that lots of votage was probably dropped across the wires anywhere ? I think I forgot to if you did nee to mention that :/

Reply 6

I don't think you had to mention that, I'm pretty sure you only had to talk about the voltage drop across the LED and diode. The circuit was pretty much: (in series)

9V supply -> LED -> Diode -> Resistor -> 0V

And you had to calculate the voltage across the resistor.

You were told the forward voltage of the LED was 2V and you have to make the assumption yourself of the forward voltage of the diode (I assumed 0.7V dropped). Then 9V-2V-0.7V = Voltage drop across the resistor = 6.3V

I'm not sure what they allow for your assumption of voltage dropped across diode though - they may be quite lenient if the calculation is correct. I think this is right anyway...I could be wrong about my own answer!

Reply 7

Adjon is right :smile:

The voltage drop of a diode is is the data sheet provided so it will be marked for exactly 6.3V.

Reply 8

I hadn't even realised it was in the datasheet but thank goodness I guessed correctly!

Reply 9

yeah The only two bits I messed up were taking into account the voltage drop of the diode and earlier on in the systems question what was the subsystem and then the semiconductor used in that subsystem ?

Reply 10

I said that the subsystem was a Comparator and the semiconductor for that was an Op-Amp. The majority in my school also put the same as me. You'll have only lost a couple of marks though :smile:

Reply 11

Sounds about right, when it said semiconductor I put MOSFET But never mind, I know a few of the guys in my class messed up the logic question at the end and the stack comparators so I should be ok so long as I stay above 60 marks. What do you reckon we will be drawing in ELEC2 ? I'm wondering if it will be a push pull amp for the first time ever?

Reply 12

Someone in my class put MOSFET for the semiconductor, they might accept that in the mark scheme you never know! The stacked comparators had me confused at first but it wasn't too bad really when you thought about it enough! :P As for the logic one that was quite unusual, they're normally a bit easier than that but oh well. Ahah, yeah no doubt there'll be a push-pull in ELEC2 but I'm not sure about the rest, they threw a bridge amplifier in last year which no one had ever seen before!! :s-smilie:

I'm fairly certain there will be a question where we have to connect the pins of a mono/astable and possibly an output to a MOSFET/transistor to power a lamp or motor - they like them sort of questions.

Reply 13

yeah I thought that they were for motor control haha. By the way if I have an op amp and a pushpull amplifier how do I calculate the power gain in practice? I know how to do it for theoretical power gain. I also know that I need to be taking into account the voltage drop across the FET which I can but I don't know how to include the max output voltage of the op amp in the calculation. http://filestore.aqa.org.uk/subjects/AQA-ELEC2-W-QP-JUN10.PDF it is Q6 part c of this paper. I can correctly calculate theoretical power gain to be 9W. but finding the gain in practice escapes me, the mark scheme says 5W. Any help would we greatly appreciated.

Reply 14

Sorry I've been thinking about it on and off all day and I can't get my head around it either...I would assume that you would get the mark for saying "It's theoretical power is 9W and he needs a minimum of 5W hence this is suitable." - not sure whether it's accepted or not though...

As for the logic question, it always seems to be an EX-OR! It must be one of the nicest to recognise and make with other gates. Boolean algebra is ok but I prefer representing it with Karnaugh maps, easier for me to interpret.

Reply 15

znq

Can anyone remember what each question was about?

I can remember off the top of my head the logic question at the start, the op-amp question, the zener question, and the big logic one at the end, but nothing else!

I'm one of those people who appears to suffer from 'post-exam amnesia', but for all exams except maths xD

Reply 16

Can't remember the order but there were 2 logic questions, a systems question, a comparator question, the question about the diodes and the zener question I think that was all ? 6 questions I think I remeber seeing a 6 on the last question haha

(edited 10 years ago)

Reply 17

For your question yesterday James - When I did this paper I calculated the realistic power to be 9W and then wrote "suitable", then I calculated the realistic power to be 6.25W and then wrote "suitable" next to it. My teacher marked this as correct so I'm guessing that's all you had to do for the 3 marks.

Reply 18

How did you calculate the realistic power to be 6.25W?

Reply 19