## Circuit Lab B/C

Cathy-TJ
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### Re: Circuit Lab B/C

mjcox2000 wrote: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.
Voltage = $10^-^4 (R+2)+3.2$  Volts

Min R = $[(V-3.2)/10^-^2]-2$ Ohms
Max R = $[(V-3.2)/10^-^4]-2$ Ohms
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mjcox2000
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### Re: Circuit Lab B/C

Cathy-TJ wrote:
mjcox2000 wrote: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.
Voltage = $10^-^4 (R+2)+3.2$  Volts

Min R = $[(V-3.2)/10^-^2]-2$ Ohms
Max R = $[(V-3.2)/10^-^4]-2$ Ohms
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Cathy-TJ
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### Re: Circuit Lab B/C

What are the values of R3 and R4 if you want the battery to supply 83.3 mA to the circuit while the ammeter reads 0.00mA?

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mjcox2000
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### Re: Circuit Lab B/C

Cathy-TJ wrote:What are the values of R3 and R4 if you want the battery to supply 83.3 mA to the circuit while the ammeter reads 0.00mA?

The 0 current condition requires that $\frac{R_3}{R_4}=\frac{20}{280}$, and the 83.3mA current condition requires that the total parallel resistance be $180\Omega$, so $R_3+R_4=450\Omega$, so $\boxed{R_3=30\Omega,\ R_4=420\Omega}$.
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Cathy-TJ
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### Re: Circuit Lab B/C

mjcox2000 wrote:
Cathy-TJ wrote:What are the values of R3 and R4 if you want the battery to supply 83.3 mA to the circuit while the ammeter reads 0.00mA?

The 0 current condition requires that $\frac{R_3}{R_4}=\frac{20}{280}$, and the 83.3mA current condition requires that the total parallel resistance be $180\Omega$, so $R_3+R_4=450\Omega$, so $\boxed{R_3=30\Omega,\ R_4=420\Omega}$.
You're correct!
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### Re: Circuit Lab B/C

Restarting... what force is exerted between two protons one meter apart?

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### Re: Circuit Lab B/C

UTF-8 U+6211 U+662F wrote:Restarting... what force is exerted between two protons one meter apart?
Using Coulomb's law and knowing protons are elementary charges.... F = (9x10^9)(1.6x10^-19)(1.6x10^-19) / (1)^2... Would the answer be 2.30x10-28 N?
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### Re: Circuit Lab B/C

krasabnk wrote:
UTF-8 U+6211 U+662F wrote:Restarting... what force is exerted between two protons one meter apart?
Using Coulomb's law and knowing protons are elementary charges.... F = (9x10^9)(1.6x10^-19)(1.6x10^-19) / (1)^2... Would the answer be 2.30x10-28 N?

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### Re: Circuit Lab B/C

C Only

Given this orientation of an operational amplifier, find the value of Rf (in kΩ) if the Vin = 20 mV, Rg = 3.8 kΩ, and Vout = 64 mV
(sorry for my bad drawing, haha)
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### Re: Circuit Lab B/C

krasabnk wrote:
Given this orientation of an operational amplifier, find the value of Rf in kΩ if the Vin = 20 mV, Rg = 3.8 kΩ, and Vout = 64 mV
(sorry for my bad drawing, haha)
I love this drawing
8.36 kiloohms?

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