## Circuit Lab B/C

Cathy-TJ
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State: VA

### Re: Circuit Lab B/C

Calculate the resistance between terminals A and B in the infinite chain of resistors where all resistors are 1 ohm.
Since the network repeats, if its resistance is R, it consists of a 1-ohm resistor in series with a unit consisting of a parallel 1-ohm and R-ohm resistor. Solving for R, we see that $R=\frac{1+\sqrt5}2\Omega$, or assuming sufficient sig figs, about $1.618\Omega$.
Nice!
The answer is also the golden ratio!
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mjcox2000
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State: VA

### Re: Circuit Lab B/C

Positive and negative charge carriers behave the same in almost all circuits. However, there are some circuits in which it actually makes a difference whether charge carriers are positive or negative. What is an example of a circuit in which this matters, and why does the distinction matter for this circuit?
MIT ‘23
TJHSST ‘19
Longfellow MS
2019:
Circuit Lab: 1st
Thermodynamics: 2nd
Sounds of Music: 5th
Mission Possible: 6th

2018:
Code Busters (trial): 1st

2015:
Simple Machines: 2nd
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2014:
WIDI: 2nd
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Cathy-TJ
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Posts: 28
Joined: January 20th, 2019, 7:13 pm
Division: C
State: VA

### Re: Circuit Lab B/C

Positive and negative charge carriers behave the same in almost all circuits. However, there are some circuits in which it actually makes a difference whether charge carriers are positive or negative. What is an example of a circuit in which this matters, and why does the distinction matter for this circuit?
N-gate and P-gate transistors? P gates allow flow when the signal is low (logic 0), while N-gates allow flow when the signal is high (logic 1).
Might be misinterpreting this question.
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mjcox2000
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Posts: 120
Joined: May 9th, 2014, 3:34 am
State: VA

### Re: Circuit Lab B/C

Positive and negative charge carriers behave the same in almost all circuits. However, there are some circuits in which it actually makes a difference whether charge carriers are positive or negative. What is an example of a circuit in which this matters, and why does the distinction matter for this circuit?
N-gate and P-gate transistors? P gates allow flow when the signal is low (logic 0), while N-gates allow flow when the signal is high (logic 1).
Might be misinterpreting this question.
That’s not what I was going for.

Let me try rephrasing the question: Describe a circuit in which macro-level measurements of the circuit would differ depending on whether charge carriers are electrons flowing opposite conventional current or positive charge carriers flowing in the direction of conventional current.
MIT ‘23
TJHSST ‘19
Longfellow MS
2019:
Circuit Lab: 1st
Thermodynamics: 2nd
Sounds of Music: 5th
Mission Possible: 6th

2018:
Code Busters (trial): 1st

2015:
Simple Machines: 2nd
SumoBots (trial): 2nd

2014:
WIDI: 2nd
Simple Machines: 3rd

Cathy-TJ
Member
Posts: 28
Joined: January 20th, 2019, 7:13 pm
Division: C
State: VA

### Re: Circuit Lab B/C

Positive and negative charge carriers behave the same in almost all circuits. However, there are some circuits in which it actually makes a difference whether charge carriers are positive or negative. What is an example of a circuit in which this matters, and why does the distinction matter for this circuit?
N-gate and P-gate transistors? P gates allow flow when the signal is low (logic 0), while N-gates allow flow when the signal is high (logic 1).
Might be misinterpreting this question.
That’s not what I was going for.

Let me try rephrasing the question: Describe a circuit in which macro-level measurements of the circuit would differ depending on whether charge carriers are electrons flowing opposite conventional current or positive charge carriers flowing in the direction of conventional current.
A circuit that uses Hall effect, since changing the charge carrier would reverse the voltage produced.
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mjcox2000
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Posts: 120
Joined: May 9th, 2014, 3:34 am
State: VA

### Re: Circuit Lab B/C

N-gate and P-gate transistors? P gates allow flow when the signal is low (logic 0), while N-gates allow flow when the signal is high (logic 1).
Might be misinterpreting this question.
That’s not what I was going for.

Let me try rephrasing the question: Describe a circuit in which macro-level measurements of the circuit would differ depending on whether charge carriers are electrons flowing opposite conventional current or positive charge carriers flowing in the direction of conventional current.
A circuit that uses Hall effect, since changing the charge carrier would reverse the voltage produced.
MIT ‘23
TJHSST ‘19
Longfellow MS
2019:
Circuit Lab: 1st
Thermodynamics: 2nd
Sounds of Music: 5th
Mission Possible: 6th

2018:
Code Busters (trial): 1st

2015:
Simple Machines: 2nd
SumoBots (trial): 2nd

2014:
WIDI: 2nd
Simple Machines: 3rd

Cathy-TJ
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Posts: 28
Joined: January 20th, 2019, 7:13 pm
Division: C
State: VA

### Re: Circuit Lab B/C

When and why would you use a Kelvin Double Bridge?
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Things2do
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Location: Unfortunately, not Utah somewhere near the Colorado border

### Re: Circuit Lab B/C

To measure unknown resistors under 1 Ohm?
John 5:46-47
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Is this where I put the Builder Cult?
"I think that we're all mentally ill. Those of us outside the asylums only hide it a little better - and maybe not all that much better after all." - Stephen King

Cathy-TJ
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Posts: 28
Joined: January 20th, 2019, 7:13 pm
Division: C
State: VA

### Re: Circuit Lab B/C

To measure unknown resistors under 1 Ohm?
That's right!
the resistance of the wires becomes significant
You have the next question!
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mjcox2000
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Joined: May 9th, 2014, 3:34 am
State: VA

### Re: Circuit Lab B/C

Since no one has posted a question yet:

An LED with voltage drop $3.2V$ and internal resistance $2\Omega$ is in series with a voltage $V$ and resistance $R$. The LED’s maximum rated current is $10mA$, and the minimum current at which its light is visible is $100\mu A$.

1. What is the minimum series voltage $V$ for the LED to emit visible light?
2. Given the value of $V$, write equations for the minimum and maximum value of $R$ for the LED to emit visible light without burning out.
MIT ‘23
TJHSST ‘19
Longfellow MS
2019:
Circuit Lab: 1st
Thermodynamics: 2nd
Sounds of Music: 5th
Mission Possible: 6th

2018:
Code Busters (trial): 1st

2015:
Simple Machines: 2nd
SumoBots (trial): 2nd

2014:
WIDI: 2nd
Simple Machines: 3rd