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# Lab 1-Dave Miller

last edited by 7 years, 3 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.

to limit the circuit current to 30mA, and with a Vf of 1.85V, use a 100-ohm resistor (close enough and well under the maximum current of 155mA)

(5V-1.85V)/(.03A) = 105 Ohm

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.

overdriving the LED with a higher voltage will cause it to fail.  Using a too small resistor is unwise.

c. What is the resistance range of the potentiometer?

resistance range is 0-Ohm (close to it) to 10K-Ohm

3.

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

Current flows in a continuous circuit, so the arrangement does not matter in this case

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

(9-1.85)/.03 = 238.3 Ohm

closest resistor is the 220-ohm (good enough, everyone loves the 220!)

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