## Circuit Lab B/C

UTF-8 U+6211 U+662F
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### Circuit Lab B/C

Reposting my question from General Chat

Copper has one valence electron, with a density of 8.94 grams per cubic centimeter and an atomic weight of approximately 64 grams per mole. Suppose a copper wire has a current density of 18.8 amperes per square millimeter. Find the drift velocity inside the wire.

mdv2o5
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### Re: Circuit Lab B/C

Reposting my question from General Chat

Copper has one valence electron, with a density of 8.94 grams per cubic centimeter and an atomic weight of approximately 64 grams per mole. Suppose a copper wire has a current density of 18.8 amperes per square millimeter. Find the drift velocity inside the wire.
If the answer above is right, then here's the next question:
(this one is for Div C according to the new rules)
Determine the output voltage as a function of the source voltage, R1, and R2.

A note on studying for op amps and also a bit of a hint: Ideally, inverting and non-inverting op amp configurations should be memorized/included on your notes, but it's always good to be able to derive these formulas using basic circuit laws and the ideal op amp assumptions since it's really easy to create an op amp circuit that does not fall neatly into a standard configuration.

UTF-8 U+6211 U+662F
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Posts: 1491
Joined: January 18th, 2015, 7:42 am
Division: C
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### Re: Circuit Lab B/C

Determine the output voltage as a function of the source voltage, R1, and R2.

A note on studying for op amps and also a bit of a hint: Ideally, inverting and non-inverting op amp configurations should be memorized/included on your notes, but it's always good to be able to derive these formulas using basic circuit laws and the ideal op amp assumptions since it's really easy to create an op amp circuit that does not fall neatly into a standard configuration.
Interesting introduction problem to op-amps for me!
Edit: Small error. See next post for corrected work and answer.
Last edited by UTF-8 U+6211 U+662F on September 5th, 2018, 6:05 pm, edited 1 time in total.

mdv2o5
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Posts: 19
Joined: July 9th, 2018, 7:24 am
State: IN
Location: MA

### Re: Circuit Lab B/C

Determine the output voltage as a function of the source voltage, R1, and R2.

A note on studying for op amps and also a bit of a hint: Ideally, inverting and non-inverting op amp configurations should be memorized/included on your notes, but it's always good to be able to derive these formulas using basic circuit laws and the ideal op amp assumptions since it's really easy to create an op amp circuit that does not fall neatly into a standard configuration.
Interesting introduction problem to op-amps for me!
Close! Check the KCL expression again (and remember that I = V/R)

UTF-8 U+6211 U+662F
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### Re: Circuit Lab B/C

Close! Check the KCL expression again (and remember that I = V/R)
Whoops. I always mess up Ohm's law for some reason (I should really make sure to double check).
Take two

mdv2o5
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Posts: 19
Joined: July 9th, 2018, 7:24 am
State: IN
Location: MA

### Re: Circuit Lab B/C

Close! Check the KCL expression again (and remember that I = V/R)
Whoops. I always mess up Ohm's law for some reason (I should really make sure to double check).
Take two
Looks good!
A neat little trick...

UTF-8 U+6211 U+662F
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### Re: Circuit Lab B/C

A neat little trick...
All right, thanks!

Onto basic circuit safety:
Touching two nodes of a DC voltage of above approximately what voltage can be lethal? What kind of factors affect whether a shock might be lethal? What current range is usually lethal? What are some harmful effects of having a current flow through you that is below the lethal limit (i.e. not enough to get you killed)?

Jacobi
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### Re: Circuit Lab B/C

All right, thanks!

Onto basic circuit safety:
Touching two nodes of a DC voltage of above approximately what voltage can be lethal? What kind of factors affect whether a shock might be lethal? What current range is usually lethal? What are some harmful effects of having a current flow through you that is below the lethal limit (i.e. not enough to get you killed)?

UTF-8 U+6211 U+662F
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Posts: 1491
Joined: January 18th, 2015, 7:42 am
Division: C
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### Re: Circuit Lab B/C

All right, thanks!

Onto basic circuit safety:
Touching two nodes of a DC voltage of above approximately what voltage can be lethal? What kind of factors affect whether a shock might be lethal? What current range is usually lethal? What are some harmful effects of having a current flow through you that is below the lethal limit (i.e. not enough to get you killed)?
Correct! Although, it's important to note that for current to happen, you do need a voltage. That's why you see signs like "High Voltage" on fences. The rule that current not voltage kills isn't entirely true because of this and is only a guideline. Be very wary of voltage, as it's impossible to know the resistance of your body at any given moment.

Jacobi
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### Re: Circuit Lab B/C

Write the voltage drop equations for a capacitor and a resistor.

UTF-8 U+6211 U+662F
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### Re: Circuit Lab B/C

Write the voltage drop equations for a capacitor and a resistor.
$V_C = \frac{Q}{C}$

$V_R = IR$

Jacobi
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Posts: 137
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### Re: Circuit Lab B/C

Write the voltage drop equations for a capacitor and a resistor.
$V_C = \frac{Q}{C}$

$V_R = IR$
Awesome! You next.

Jacobi
Exalted Member
Posts: 137
Joined: September 4th, 2018, 7:47 am
State: -

### Re: Circuit Lab B/C

Write the voltage drop equations for a capacitor and a resistor.
$V_C = \frac{Q}{C}$

$V_R = IR$
Awesome! You next.

UTF-8 U+6211 U+662F
Exalted Member
Posts: 1491
Joined: January 18th, 2015, 7:42 am
Division: C
State: PA

### Re: Circuit Lab B/C

Write the voltage drop equations for a capacitor and a resistor.
$V_C = \frac{Q}{C}$

$V_R = IR$
Awesome! You next.
All right!

Describe the behavior of an RC circuit which is a) charging and b) discharging.

Jacobi
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Posts: 137
Joined: September 4th, 2018, 7:47 am
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### Re: Circuit Lab B/C

All right!

Describe the behavior of an RC circuit which is a) charging and b) discharging.
a) The voltage through the resistor starts high and decays exponentially as the capacitor becomes saturated. The charged capacitor has an extremely high voltage drop.
b) The voltage through the resistor starts high and decays exponentially as the capacitor discharges. The capacitor acts as a voltage source in the absence of other sources.