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Electronics Quiz... Concerned with how accurately things were marked

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Quarta
#1
Dec11-12, 03:33 PM
P: 3
I am writing on this forum because I'm extremely troubled... I recently had a quiz in my "Project Lab" for which I just received my results.

...The entire course revolved around building a variable power supply. There was no theory class to support the lab.

...Before receiving the marked test back, I had learned that half our class (it's broken up into two sections because of size) was allowed to use the internet/google as a resource! The first half of the class which I was in was only allowed to use our notes. ...I was quite frustrated by this and brought my concerns to the teacher... to which he responded "their test was harder".... My response was "I guess we'll see when we get our results back, won't we".... Because I did not feel comfortable with my answers at all after writing it, and I believe that half the class had an unfair advantage, no matter how much harder their test was.... With a resource like Google and the internet you can do quite a lot in 2 hours! ...while our only resources were what we brought to class with us.

....Enough students complained... The teacher told us today that there was a 2% higher average for the part of the class which was allowed to use Google to find answers on the test, so that 2% was added to the first half of the classes total marks.

Well... I received my test back today, and am extremely disappointed with the results.... I have attached a copy of the entire test for people to review... I am actually quite concerned that some of the questions were WAY too vague, and in some cases marked incorrectly.

Here is the Quiz (which is actually worth 15% of our course mark!) ....it's horribly written but it looks like my final mark was 9/17

page1


page2


I realize that I made some legitimate errors... However without a resource like the INTERNET it was the best I could do.... And I do have some concerns with the questions and the way that they were marked, and would like a second opinion (or many).

Question 1.... If you reverse the leads on a potentiometer (the one that controls voltage on the variable power supply) ...you would change the direction in which it needs to be turned to increase or decrease voltage.... Am I not correct?... can anyone see why I got that wrong?!

Question 3.... This question pertains to Soldering paste. It asks to circle the most correct answer. (which A and B are very similar) .... My reasoning for picking "A" was because I have the understanding that the danger with solder is the cumulative effect of lead in the human body... (which is much more serious than temporary harm to your lungs) ...here is an example of Solder Paste MSDS proving my point http://www.gcelectronics.com/order/msds/123.pdf

Question 8.... It simply asks to state ONE purpose of the ground terminal in a power supply...(as described in question 7) .... HOW is my answer incorrect?!

...the rest of the questions/errors are probably legitimate... Although questionable as to whether it was ever taught in class... I do have a particular issue with Question 12) b. ....HOW does a capacitor INCREASE voltage in a circuit!? WHY would the voltage ever be greater than it's input!?


...Any opinions/input would be greatly appreciated!
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justsomeguy
#2
Dec11-12, 04:06 PM
P: 166
Quote Quote by Quarta View Post
Question 1.... If you reverse the leads on a potentiometer (the one that controls voltage on the variable power supply) ...you would change the direction in which it needs to be turned to increase or decrease voltage.... Am I not correct?... can anyone see why I got that wrong?!
Can't see the diagram, but if it's a 2-post POT then no. There would be no effect. Turning the POT one way increases resistance between the posts, turning it the other way decreases the resistance. In a 3-post POT if you switched which leg the circuit was hooked up to, then your answer would be correct.

Quote Quote by Quarta View Post
Question 3.... This question pertains to Soldering paste. It asks to circle the most correct answer. (which A and B are very similar) .... My reasoning for picking "A" was because I have the understanding that the danger with solder is the cumulative effect of lead in the human body... (which is much more serious than temporary harm to your lungs) ...here is an example of Solder Paste MSDS proving my point http://www.gcelectronics.com/order/msds/123.pdf
I think you should get this one right.

Quote Quote by Quarta View Post
Question 8.... It simply asks to state ONE purpose of the ground terminal in a power supply...(as described in question 7) .... HOW is my answer incorrect?!
This should be marked correct as well.
Quarta
#3
Dec11-12, 04:19 PM
P: 3
...it was a 3 post POT. the wiper is soldered directly to one of the outer posts.

thank you for your input.... I am quite frustrated with this "Professor"

justsomeguy
#4
Dec11-12, 04:30 PM
P: 166
Electronics Quiz... Concerned with how accurately things were marked

The question asks about switching the position of the leads, not about disconnecting one lead and using the other. That may be why it's marked wrong anyway. Should be worth half a point at least!
yungman
#5
Dec11-12, 06:39 PM
P: 3,904
Quote Quote by Quarta View Post
Question 1.... If you reverse the leads on a potentiometer (the one that controls voltage on the variable power supply) ...you would change the direction in which it needs to be turned to increase or decrease voltage.... Am I not correct?... can anyone see why I got that wrong?!
It is a funny question, you must have a diagram of the original pot that I don't know, I can't even answer this question. Can't help you on this.

Question 3.... This question pertains to Soldering paste. It asks to circle the most correct answer. (which A and B are very similar) .... My reasoning for picking "A" was because I have the understanding that the danger with solder is the cumulative effect of lead in the human body... (which is much more serious than temporary harm to your lungs) ...here is an example of Solder Paste MSDS proving my point http://www.gcelectronics.com/order/msds/123.pdf
Well, if it is extremely hazel to people, they would not have allow people to use it. So it is more like harmful if smells too much.

Question 8.... It simply asks to state ONE purpose of the ground terminal in a power supply...(as described in question 7) .... HOW is my answer incorrect?!
The last thing you want is to conduct current during electrocution!! It's the current that kill the person, not the voltage.
...the rest of the questions/errors are probably legitimate... Although questionable as to whether it was ever taught in class... I do have a particular issue with Question 12) b. ....HOW does a capacitor INCREASE voltage in a circuit!? WHY would the voltage ever be greater than it's input!?


...Any opinions/input would be greatly appreciated!
I don't like these questions at all.
0xDEADBEEF
#6
Dec11-12, 07:09 PM
P: 825
Q3 For all practical purposes solder fumes do not contain led but only flux fumes, so I don't see why effects should accumulate.

Q8 Your answer is misleading. The electrocution is not prevented, by supplying a return path. It is prevented by putting the chassis at ground potential, or by supplying a return path that is closer to hot leads then a human and consequently causing a circuit breaker or an RCD to go off, but I think this is the 0 point answer that is the least false.

Q12 Read about ripple on wikipedia http://en.wikipedia.org/wiki/Ripple_%28electrical%29, and understand the difference between peak voltage and rms voltage. Capacitors can charge up to the peak voltage not just the rms voltage.
davenn
#7
Dec11-12, 07:48 PM
Sci Advisor
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P: 2,748
The Q9, RoHS you got wrong because in solder under the RoHS laws has NO lead in it, so there is no tin/lead ratio to consider
If you look on RoHS circuit boards, you will find a circle with Pb ( lead symbol) with a slash through it .... NO Lead :)

Dave
davenn
#8
Dec11-12, 08:06 PM
Sci Advisor
PF Gold
davenn's Avatar
P: 2,748
Also on Q12 ...

you DONT get smooth DC out of a bridge rectifier ;)



you dont even get smooth, flatlined DC out of a bridge rectifier with a smoothing capacitor ...

see the link you were given above for the ripple waveform

cheers
Dave
Attached Thumbnails
fullwave rectification waveform.jpg  
the_emi_guy
#9
Dec11-12, 11:17 PM
P: 589
They gave you 2 hours for this!? Looks to me like a 15-20 minute quiz.

Ground connections are one of the ways human safety are provided in electrical equipment, but you would certainly not put a ground terminal on the front of the unit whose connectivity was required for human safety.

Sorry, but this does not look like a hard quiz to me, and I would think that surfing the Internet would just slow you down.

Sounds like you are not really learning what you should in this class. Maybe the teachers fault, maybe your fault, maybe some of both?
Quarta
#10
Dec11-12, 11:26 PM
P: 3
Quote Quote by the_emi_guy View Post
They gave you 2 hours for this!? Looks to me like a 15-20 minute quiz.

Ground connections are one of the ways human safety are provided in electrical equipment, but you would certainly not put a ground terminal on the front of the unit whose connectivity was required for human safety.

Sorry, but this does not look like a hard quiz to me, and I would think that surfing the Internet would just slow you down.

Sounds like you are not really learning what you should in this class. Maybe the teachers fault, maybe your fault, maybe some of both?
if we were actually taught any of the material in class I would totally agree with you, my average in DC theory is 97 percent, all the rest of my course marks are high... believe me, it had nothing to do with a lack of studying, almost everything on that quiz was the first time I had ever seen the material.

I will be getting the students together from my section and filing a formal complaint with the program coordinator.

thank you all for your advice/answers/opinions... they made a lot of sense now that it was explained to me
yungman
#11
Dec11-12, 11:40 PM
P: 3,904
I have to say the questions are pretty bad.


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