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Lab 1 Questions (Wiki page)

Page history last edited by zahraa@... 5 years, 1 month ago

Lab 1 Questions:

Part C:

2A. 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.

  • 100 olm resistance is required to limit current to 30 mA red LED and 120 olm resistance for 25 mA yellow and green LEDs.


How do you get it??   -0.5

R should be R = (Vcc - Vf) / I      

2B. 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 the minimum resistance because if you made the resistance lower the LED would fail; the voltage would be too high and would cause the LED to short out.



2C. What is the resistance range of the potentiometer?

  • The resistance range of the potentiometer is from 0 olms to 100 olms.

It should be about 10K  -0.5



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

  • The order of the components of my circuit matters because I cannot have my LED come before the resistor; the LED requires a resistor to come before it in order to diffuse some of the voltage and prevent the LED from shorting out. The potentiometer must come before the LED in order to change the voltage before it reaches the LED. The switch, however, can be placed anywhere in the circuit.


No, the order doesn’t matter 

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

  • The minimum resistance required for use with my LED if I was using a 9 volt battery is 220 olms resistance for a 30 mA red LED and 270 olms resistance for 25 mA yellow and green LEDs.


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