Shock Value B/Circuit Lab C

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geminicross
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Re: Shock Value B/Circuit Lab C

Post by geminicross » February 12th, 2013, 5:21 pm

Well I guess it's time to see how much I can learn in 4 days then :P.

(BTW: I put in some information on Wheastone Bridges in my binder just in case. )

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Re: Shock Value B/Circuit Lab C

Post by Bozongle » February 12th, 2013, 5:22 pm

geminicross wrote:Well I guess it's time to see how much I can learn in 4 days then :P.

(BTW: I put in some information on Wheastone Bridges in my binder just in case. )
If I were you get experience with magnets and actualy building circuits and using multimeters, hands-on tasks (Actually messing with real circuits) is usually 50% of the event, and magnets are a pretty big part too.

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Re: Shock Value B/Circuit Lab C

Post by geminicross » February 12th, 2013, 5:26 pm

Bozongle wrote:
geminicross wrote:Well I guess it's time to see how much I can learn in 4 days then :P.

(BTW: I put in some information on Wheastone Bridges in my binder just in case. )
If I were you get experience with magnets and actualy building circuits and using multimeters, hands-on tasks (Actually messing with real circuits) is usually 50% of the event, and magnets are a pretty big part too.
I know, but I wont be able to access that stuff till Thurs.

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Re: Shock Value B/Circuit Lab C

Post by cyanophycean314 » February 12th, 2013, 5:27 pm

For those who would like another resource, All About Circuits is a great site where they provide free textbooks for circuitry. It teaches you everything from basic concepts of voltage and current, series/parallel, kirchoff's, network analysis, capacitors and beyond. The one potential downside is that it uses electron current, which may be confusing to those who have learned circuits with convential current.

Overall, it is a great site with lots of great info. Here is a link to volume 1: http://www.allaboutcircuits.com/vol_1/index.html
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Re: Shock Value B/Circuit Lab C

Post by Bozongle » February 12th, 2013, 5:31 pm

cyanophycean314 wrote:For those who would like another resource, All About Circuits is a great site where they provide free textbooks for circuitry. It teaches you everything from basic concepts of voltage and current, series/parallel, kirchoff's, network analysis, capacitors and beyond. The one potential downside is that it uses electron current, which may be confusing to those who have learned circuits with convential current.

Overall, it is a great site with lots of great info. Here is a link to volume 1: http://www.allaboutcircuits.com/vol_1/index.html
The link you listed seems to be the same book as a resource on the SoInc page
http://www.ibiblio.org/kuphaldt/electri ... index.html

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Re: Shock Value B/Circuit Lab C

Post by tangentline » February 12th, 2013, 6:30 pm

cyanophycean314 wrote:For those who would like another resource, All About Circuits is a great site where they provide free textbooks for circuitry. It teaches you everything from basic concepts of voltage and current, series/parallel, kirchoff's, network analysis, capacitors and beyond. The one potential downside is that it uses electron current, which may be confusing to those who have learned circuits with convential current.

Overall, it is a great site with lots of great info. Here is a link to volume 1: http://www.allaboutcircuits.com/vol_1/index.html
Wow, you got 1st and 3rd at circuits at an invitational! It's certainly a great website that helps you learn the theoretical. I've been involved in working with a school from a different state writing practice tests and I just have to say I'm surprised at some of the things that a 1st place overall at regionals team does not know (that can be pulled from that website)!

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Re: Shock Value B/Circuit Lab C

Post by wjnewhouse » February 12th, 2013, 6:53 pm

Hi, I had a question about a hands-on circuit lab problem I had at regionals (Bethel University, Minnesota; 1/26/13). My question isn't about actually finding an answer, but about the actual question and the parameters of what we were allowed to do. Here's the problem:

A wheatstone bridge was set up for us and was connected to a power supply (it was supplying a certain voltage; I can't remember how much).

Image

We were given the resistor values of R_1 and R_3. R_2 was a potentiometer. The problem was asking for us to find the value of the unknown resistor R_x. We were also given a multimeter that could measure voltage and ampage.

Looking back on the problem, we know how we could have found the answer if we would know the resistance of the potentiometer at certain positions (we would measure the voltage across the points D and B, then adjust the potentiometer until the voltmeter read zero, then we would know the ratios (R_1)/(R_2)=(R_3)/(R_x) ). But there was no way to know the resistance of the potentiometer just by looking at it. What I'm asking is this: Does anyone know what measurements we were allowed to take with the multimeter? We could of just used the multimeter to measure voltage across and the current through R_x to calculate the resistance of R_x, but of course that defeats the purpose of the bridge (and would be cheating?).

We figure we could have measured the voltage across the potentiometer and the current going through it to calculate the resistance of the potentiometer. Does that sound like a fair way to use the multimeter?

We ended up not dedicating much time to this problem because time was running out and we needed to work on our written problems, so we didn't ask the supervisors any questions concerning this.
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Re: Shock Value B/Circuit Lab C

Post by tangentline » February 12th, 2013, 8:09 pm

I'm not technically sure if you can measure the current of that circuit... Without taking it apart...

Was there a way to determine the resistance of the potentiometer such as a maximum and a minimum resistance? Then you can do your circuit analysis techniques :)
Or I'd do voltage division if that thing in the middle isn't there.

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Re: Shock Value B/Circuit Lab C

Post by chalker » February 12th, 2013, 8:36 pm

tangentline wrote:I'm not technically sure if you can measure the current of that circuit... Without taking it apart...

Was there a way to determine the resistance of the potentiometer such as a maximum and a minimum resistance? Then you can do your circuit analysis techniques :)
Or I'd do voltage division if that thing in the middle wasn't there.

You technically can measure current in wires without disconnecting them with a clamp-on ammeters, but that's not needed here. Using the voltage across R3, and the known resistance of R3, you can calculate the current through Rx (assuming you've adjusted the potentiometer to make Gx read 0 current). Check out the wikipedia page for more details: http://en.wikipedia.org/wiki/Wheatstone_bridge

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Re: Shock Value B/Circuit Lab C

Post by iwonder » February 12th, 2013, 8:40 pm

But wouldn't you need to know the resistance of R3 to use the standard method like what you mention, chalker? I think the intent was to adjust the potentiometer to a known resistance(0 would be good, maybe the max of the device is known) and then measure the voltage difference and calculate Rx from there(this method is also detailed on the wikipedia page).
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