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Jeffery Yang Lab 1

Page history last edited by zahraa@... 5 years, 3 months ago


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.

Red: 1.8 V forward voltage drop


R = (5V - 1.8 V)/ 0.030 A

R = 107 ohms

Green: 2.1 V forward voltage drop


R = (5V - 2.1 V)/ 0.025 A

R = 116 ohms


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.

Minimum; if you lowered resistance, the LED could fail.


c. What is the resistance range of the potentiometer?

about 10 kOhms



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

yes; if you put the led before the resistor, then it could fail because the resistor is meant to reduce current before electricity reaches the led.

No, The order doesn’t matter



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

Green LED: 2.1 V forward voltage drop


R=(9V-2.1V)/0.025 A

R=276 ohms












Comments (1)

zahraa@... said

at 5:04 pm on Jul 6, 2015

Good Job

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