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Emily Wong Lab 1

Page history last edited by zahraa@... 5 years ago

Used a 180 ohm resistor


1. 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.


5 volts in

0.025 A limit

2.5 forward voltage drop according to data sheet


R = (Vin - VF)/I


Resistance should be 100 ohms if using a green LED.



2. 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, resistance and current are inversely proportional. A higher resistance would mean a smaller current, which the LED could take. However, a lower resistance would lead to a larger current, which could potentially cause the LED to fail.


3. What is the resistance range of the potentiometer?


Using a multimeter, the resistance range of the potentiometer was found to be from 0 to about 10 kilo-ohms.


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


The order that the components of the circuit are arranged between power and ground does not matter because the current that runs through a circuit that is connected in series is constant through all the components.

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


R = (Vin - VF)/I


With a 9 volt battery, the minimum resistance required for use with a green LED would be 260 ohms.

6. Video


Comments (1)

zahraa@... said

at 5:02 pm on Jul 6, 2015

Great Job

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