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Stewart_Gray Lab Report 1

Page history last edited by Vivien Tsao 7 years, 2 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.

Given that the current is being supplied with 5V, and the forward voltage of the LED is 1.85V, the current needs a minimum resistance of 105ohms to prevent the LED from exceeding its maximum DC forward current rating.



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.

 105ohms is the minimum resistance needed to safely allow the current to flow through the LED. 


c. What is the resistance range of the potentiometer?

The resistance of the potentiometer ranges from 0k to 10kohms (But will leave the current with a minimum resistance of 150ohms regardless).


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

Yes, the order would matter as a resistor must always be connected to the rail before reaching the LED.

-0.5 Is this true? Look at the voltage drops across each component in the reversed arrangement!


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

With a 9V battery, the minimum resistance required to use the LED would be approximately 238ohms.


Video of the lab in motion:









Comments (1)

Vivien Tsao said

at 5:55 pm on Jul 11, 2013

Good job!

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