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Song Mingxun Lab 1

Page history last edited by zahraa@... 4 years, 12 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.

I am using a yellow LED which has a forward voltage of 2.4 volts. By using the equation (Vs-Vf)/Current = resistance, I found that the resistance is 104 ohm. 5V-2.4=2.6V 2.6V/0.025 amp = 104 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.

The resistance from the previous question is the minimum resistance. This is because we are trying to limit the maximum current 25 mA. Since the current and the resistance are in inverse relationship, you need the minimum current in order to limit the maximum current.

 

c. What is the resistance range of the potentiometer?

By using the multimeter, I found the resistance range of the potentiometer is  from 10.27 k ohm to 0 ohm.

 

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

It does not matter what order the components are arranged between power and ground. This is because the circuit is in series and the current is the same at every single point. If the current is the same throughout, there is no danger overpowering the LED. Furthermore, the voltage changes but in this case, the voltage doesn't matter.

✔ 

 

 

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

By using the equation (Vs-Vf)/Current = resistance, I found that the minimum resistance is 264 ohm. 9V-2.4V=6.6V 6.6V/0.026 amp = 264 ohm.

✔ EXCELLENT

 

 


Comments (2)

zahraa@... said

at 4:08 pm on Jul 6, 2015

Great Job

zahraa@... said

at 4:08 pm on Jul 6, 2015

Great Job

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