## Shock Value B/Circuit Lab C

Unbihexium
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### Re: Shock Value B/Circuit Lab C

Infinity Flat wrote:
Unbihexium wrote:
Toms_42 wrote:Oops, I meant "multilooped. It autocorrected it 0.o

As in, circuits with multiple batteries. Can someone explain why the loop and current directions when using kirkhoffe's rules are arbitrary?

Because if you choose the direction to be wrong, you'll simply end up with a negative current. However, you should avoid kirchhoff's rules in circuit analysis as they result in horrendous systems of equations to solve, so instead learn the node voltage and mesh current analysis method, they reduce the number of equations and make your life easier. They are simply more simplified versions of kirchhoff's laws intended for analysis.

If your only issue is multiple batteries, I think its easier to do superposition with the batteries. But really just do whatever you're most comfortable with.

Super position is great if you have 2 batteries... it gets messy because when you need to solve a circuit since you have 4 batteries 4 times, its better to use node, usually faster than superposition. Also superposition only works in linear element networks
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fourLoko
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### Re: Shock Value B/Circuit Lab C

Unbihexium wrote:
Unbihexium wrote:
Toms_42 wrote:Oops, I meant "multilooped. It autocorrected it 0.o

As in, circuits with multiple batteries. Can someone explain why the loop and current directions when using kirkhoffe's rules are arbitrary?

Because if you choose the direction to be wrong, you'll simply end up with a negative current. However, you should avoid kirchhoff's rules in circuit analysis as they result in horrendous systems of equations to solve, so instead learn the node voltage and mesh current analysis method, they reduce the number of equations and make your life easier. They are simply more simplified versions of kirchhoff's laws intended for analysis.

Super position is great if you have 2 batteries... it gets messy because when you need to solve a circuit since you have 4 batteries 4 times, its better to use node, usually faster than superposition. Also superposition only works in linear element networks

I wouldn't expect a B Division test to have anything THAT horrendous. So just superposition would probably be sufficient.

Does anyone have any links/resources to learn about nonlinear circuits? I doubt I'll ever see one on a test, but better safe than sorry
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Toms_42
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### Re: Shock Value B/Circuit Lab C

fourLoko wrote:
Unbihexium wrote:
Unbihexium wrote:
Because if you choose the direction to be wrong, you'll simply end up with a negative current. However, you should avoid kirchhoff's rules in circuit analysis as they result in horrendous systems of equations to solve, so instead learn the node voltage and mesh current analysis method, they reduce the number of equations and make your life easier. They are simply more simplified versions of kirchhoff's laws intended for analysis.

Super position is great if you have 2 batteries... it gets messy because when you need to solve a circuit since you have 4 batteries 4 times, its better to use node, usually faster than superposition. Also superposition only works in linear element networks

I wouldn't expect a B Division test to have anything THAT horrendous. So just superposition would probably be sufficient.

Does anyone have any links/resources to learn about nonlinear circuits? I doubt I'll ever see one on a test, but better safe than sorry

I'll just use my calc for linear. thanks. Kirkhoffe's will suffice for now

Unbihexium
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### Re: Shock Value B/Circuit Lab C

Toms_42 wrote:
Unbihexium wrote:
Unbihexium wrote:

Super position is great if you have 2 batteries... it gets messy because when you need to solve a circuit since you have 4 batteries 4 times, its better to use node, usually faster than superposition. Also superposition only works in linear element networks

I wouldn't expect a B Division test to have anything THAT horrendous. So just superposition would probably be sufficient.

Does anyone have any links/resources to learn about nonlinear circuits? I doubt I'll ever see one on a test, but better safe than sorry

I'll just use my calc for linear. thanks. Kirkhoffe's will suffice for now

I use it too, but I'd rather type 1 equations for each 3 into my calculator, as the buttons are tiny and annoying.
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fourLoko
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### Re: Shock Value B/Circuit Lab C

Just a question before my state competition

http://www.princeton.edu/~aqu/Scioly/pr ... l/exam.pdf

I was looking at problem 8 in section 2, where it asks which range the voltmeter should be set on. I always thought ideal voltmeters had infinite resistance, so I would go with range 300, but the answer is 15. Could anyone help explain?
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iwonder
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### Re: Shock Value B/Circuit Lab C

The battery is a 12v battery, so to get the most precision from the voltmeter you would want to use the 15v range. It'd give the most precise reading without possibly over loading the meter.
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Unbihexium
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### Re: Shock Value B/Circuit Lab C

fourLoko wrote:Just a question before my state competition

http://www.princeton.edu/~aqu/Scioly/pr ... l/exam.pdf

I was looking at problem 8 in section 2, where it asks which range the voltmeter should be set on. I always thought ideal voltmeters had infinite resistance, so I would go with range 300, but the answer is 15. Could anyone help explain?

Its not an ideal Voltmeter. Its an actual one, and if you've handled a multimeter before, you'd notice that you have to set a range, which accordingly adjusts how much the circuit can measure, simply because, in reality, there's no such thing as an ideal voltmeter, so you end up changing resistance to maintain accurate measurements and each different voltage level uses different circuits. Usually ranges go something like this: 2V, 20V, 200V, 2000V, so you generally want to choose the one with the closest order of magnitude to your expected voltage, aka it has to be larger, but minimally so, so if you have a 9 volt battery, you're stuck with the 20 volt setting to not overload the voltmeter, but if you have say a AA battery, and you want to measure the voltage of that, the 2V setting works too, while higher settings would show you less decimal places.
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Toms_42
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### Re: Shock Value B/Circuit Lab C

Quick question:

When do I know whether I'm looking at conventional or electron flow? Especially in solenoid a and right hand rules and such. They all give arrows indicating flow direction, but few diagrams say whether that is electron or conventional, and this gets quite confusing. I have found diagrams that contradict each other. Is ther one I should assume? And could someone maybe point me to diagrams that do specify? Thanks.

iwonder
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### Re: Shock Value B/Circuit Lab C

Best idea is probably to ask the ES during the test if you're unsure. But typically arrows refer to current flow in my experience. Remember that right hand rules all refer to current flow as well.
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Toms_42
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### Re: Shock Value B/Circuit Lab C

iwonder wrote:Best idea is probably to ask the ES during the test if you're unsure. But typically arrows refer to current flow in my experience. Remember that right hand rules all refer to current flow as well.

I assume you mean conventional flow when you say current flow? Thanks. Right hand rules use conventional flow.

Toms_42
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### Re: Shock Value B/Circuit Lab C

I'm finalizing my binder for our state competition in PA, and I was wondering if anyone would like to share some of the harder questions they've been asked

cyanophycean314
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### Re: Shock Value B/Circuit Lab C

Toms_42 wrote:I'm finalizing my binder for our state competition in PA, and I was wondering if anyone would like to share some of the harder questions they've been asked

We had a very interesting problem. In the problem, there is an arrangement of resistors, but you don't know how they're arranged. Then they take out each resistor and tell you the value of the currents passing through each of the other resistors. Using this info, you find the value/arrangement of all the resistors. You use your basic series/parallel concepts to find the configuration and then you can find the values. In the end, it was not that hard because all the resistors had the same value
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UQOnyx
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### Re: Shock Value B/Circuit Lab C

Our NJ tiebreaker question was that there was a speaker and resistor set up in series. The value of the resistor was not known and the question was that if 4 exact same resistors were wired in parallel instead of that single resistor, would the speaker be louder or lower or no change at all (ie would the current be higher?)
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Toms_42
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### Re: Shock Value B/Circuit Lab C

UQOnyx wrote:Our NJ tiebreaker question was that there was a speaker and resistor set up in series. The value of the resistor was not known and the question was that if 4 exact same resistors were wired in parallel instead of that single resistor, would the speaker be louder or lower or no change at all (ie would the current be higher?)

fantasyfan
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### Re: Shock Value B/Circuit Lab C

The correct answer would be that the current would go up and the speaker would be louder because when a circuit is wired in parallel, the total resistance must be less than any of the resistors, and since V=IR, the current would go up
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