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# Lab 1 Karl Icho

last edited by 8 years, 2 months ago

2-a)  What resistance do you need to limit current to 30 mA (if using red LED) or 25 mA (if using yellow or green)? Be sure to state which color LED you are using. This resistance refers to the total resistance in series with the LED.

*If Using the RedLed:

Vled=1.8V

I=30mA

Vinitial=5.0V

Vresistor= Vin-Vled=5-1.8=3.2V

Vres.=R.I; R=V/I=3.2/0.03=106.67ohms

*If Using the YellowLed:

Vled=1.8V

I=25mA

Vinitial=5.0V

Vresistor=Vin-Vled=5-2=3V

Vres.=R.I; R=V/I=3/0.025=120ohms

b) Is the resistance from question a) a maximum or minimum resistance? That is, in which direction if you change the resistance (higher or lower) would the LED likely fail.

The resistance from question (a) is a minimum resistance. If we change the resistance to a lower range; the LED would get a current larger than 25mA or 30mA; thereby the LEDs would crash.

c)  What is the resistance range of the potentiometer?

The resistance range of the potentiometer is between:

By using the multimeter, I found that the range was approximately between 0 and 10Kohms.

3-a)  Does it matter what order the components of your circuit are arranged between power and ground? Why or why not?

No, it does not matter, because, if we put the switcher right after the LED, and we do not click the switcher, the current will not go all the way back the negative side of the generator; and thereby, the LED will not light up. And the same thing would happen if the Switcher was right befiore the LED light. If we click the switcher, the current is now released and can now go all the way to the negative side of the generator, and then the LED will light up!

✔ Good explanation. Another way to think of it is to consider that the circuit is connected in series. Therefore, the same current flows throughout the circuit and the order of the components does not matter.

4-a) Using this battery, what is the minimum resistance required for use with your LED?

If Using RedLight:

Vinitial=9.0V

I=30mA

Vled=1.8V

Vresistor=9-1.8=7.2V

Rres.=V/I=7.2/0.03=240ohms

If Using Yellow Light:

Vinitial=9.0V

I=25mA

Vled=2.0V

Vresistor=9-2=7V

Rres.=V/I=7/0.025=280ohms.

If Using Green Light:

Vinitial=9.0V

I=25mA

Vled=2.2V

Vresistor=9-2.2=6.8V

Rres.=V/I=6.8/0.025=272ohms.

### Comments (1)

#### Benjamin Tee said

at 12:10 am on Jul 11, 2012

Great job Karl! Do upload videos next time!

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