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Re: Circuit Lab B/C
Posted: November 22nd, 2018, 11:56 am
by Jacobi
antoine_ego wrote:Does anyone have any advice on how to design/run the practical portion? In particular, what tasks are common and how many is typical?
I haven't been to any tournaments, but I would expect problems involving applications of Kirchhoff's laws to determine resistances/capacitances. In addition, designing a circuit on a breadboard to meet certain specifications, or troubleshooting a circuit could all be possibilities.
Re: Circuit Lab B/C
Posted: December 16th, 2018, 6:11 am
by Pastaman202
Jacobi wrote:antoine_ego wrote:Does anyone have any advice on how to design/run the practical portion? In particular, what tasks are common and how many is typical?
I haven't been to any tournaments, but I would expect problems involving applications of Kirchhoff's laws to determine resistances/capacitances. In addition, designing a circuit on a breadboard to meet certain specifications, or troubleshooting a circuit could all be possibilities.
At the one competition I have been to, we were asked to find resistance using band codes. I would expect things like how to use multi-meters in the future.
Re: Circuit Lab B/C
Posted: January 2nd, 2019, 2:24 pm
by Crimesolver
Can someone explain this to me? The answer is 2 amps but I have no idea how to get that answer.
https://drive.google.com/file/d/1FDlON7 ... sp=sharing
Re: Circuit Lab B/C
Posted: January 2nd, 2019, 2:28 pm
by neerja.shah
I'm pretty new to this topic as well,
for the practical, do we just need to know how to use a multimeter or is there more.. will we have to calculate stuff from the made circuit?
also, are there any old practice tests for division b. I can only find ones from division C
thank you...
Re: Circuit Lab B/C
Posted: January 2nd, 2019, 2:50 pm
by UTF-8 U+6211 U+662F
neerja.shah wrote:I'm pretty new to this topic as well,
for the practical, do we just need to know how to use a multimeter or is there more.. will we have to calculate stuff from the made circuit?
also, are there any old practice tests for division b. I can only find ones from division C
thank you...
Try looking for Shock Value tests. The practical portion is whatever the event supervisor makes of it.
Re: Circuit Lab B/C
Posted: January 2nd, 2019, 3:46 pm
by UTF-8 U+6211 U+662F
2 amps seems too high... that's a 12 ohm resistor, so that would require 24 volts across it. The only voltage sources are 12 V and 4 V, so I'm not sure how they got that answer either.
Re: Circuit Lab B/C
Posted: January 3rd, 2019, 6:47 pm
by mdv2o5
UTF-8 U+6211 U+662F wrote:
2 amps seems too high... that's a 12 ohm resistor, so that would require 24 volts across it. The only voltage sources are 12 V and 4 V, so I'm not sure how they got that answer either.
I agree; the answer is definitely not 2A. This problem is kind of tricky in that blindly following the KVL and KCL techniques will give you the wrong answer since you end up with current flowing backwards through one of the diodes.
After some more fiddling, I got 536mA flowing through the 12ohm resistor.
Also, as a side note, 0.75V is quite low for an LED forward voltage drop. For a red LED, a typical forward voltage is closer to 1.8V.
Re: Circuit Lab B/C
Posted: January 3rd, 2019, 6:56 pm
by mdv2o5
neerja.shah wrote:I'm pretty new to this topic as well,
for the practical, do we just need to know how to use a multimeter or is there more.. will we have to calculate stuff from the made circuit?
also, are there any old practice tests for division b. I can only find ones from division C
thank you...
In the rulebook, the example task in 3.Part II.c.ii is a problem where you will have to calculate something from the circuit probably using a measurement that you need to make. The difficulty in this kind of problem probably doesn't come from actually using the multimeter but from knowing what values you need to do the calculation and then interpreting the circuit on the breadboard to make sure you're measuring the right thing. Of course, each exam will differ by how difficult the supervisor wants to make it.
Re: Circuit Lab B/C
Posted: January 3rd, 2019, 7:46 pm
by UTF-8 U+6211 U+662F
mdv2o5 wrote:UTF-8 U+6211 U+662F wrote:
2 amps seems too high... that's a 12 ohm resistor, so that would require 24 volts across it. The only voltage sources are 12 V and 4 V, so I'm not sure how they got that answer either.
I agree; the answer is definitely not 2A. This problem is kind of tricky in that blindly following the KVL and KCL techniques will give you the wrong answer since you end up with current flowing backwards through one of the diodes.
After some more fiddling, I got 536mA flowing through the 12ohm resistor.
Also, as a side note, 0.75V is quite low for an LED forward voltage drop. For a red LED, a typical forward voltage is closer to 1.8V.
I also got 536 mA, so the answer key is most likely wrong.
Re: Circuit Lab B/C
Posted: January 5th, 2019, 1:20 pm
by Crimesolver
UTF-8 U+6211 U+662F wrote:mdv2o5 wrote:UTF-8 U+6211 U+662F wrote:
2 amps seems too high... that's a 12 ohm resistor, so that would require 24 volts across it. The only voltage sources are 12 V and 4 V, so I'm not sure how they got that answer either.
I agree; the answer is definitely not 2A. This problem is kind of tricky in that blindly following the KVL and KCL techniques will give you the wrong answer since you end up with current flowing backwards through one of the diodes.
After some more fiddling, I got 536mA flowing through the 12ohm resistor.
Also, as a side note, 0.75V is quite low for an LED forward voltage drop. For a red LED, a typical forward voltage is closer to 1.8V.
I also got 536 mA, so the answer key is most likely wrong.
Thanks everyone for the input! Would you mind explaining how you got that answer?