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# Lab 1 write-up

last edited by 7 years, 6 months ago

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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.

Given Ohm's law: V=IR

I'm using a red LED, so I want to limit the current to 30 mA.

5V = 30mA * R

R = 5V / .030A

R = 166.67 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.

167 ohms is the minimum resistance. A lower resistance would allow more current to flow through the LED possibly causing it to fail, while more resistance will limit the current causing it to dim.

c. What is the resistance range of the potentiometer?

We measured the resistance range of the potentiometer to be between about 1ohm to 10kohm.

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

No it doesn't matter because the switch simply opens or closes the circuit. At any point in the circuit it will function the same either allowing current to flow through or keeping it open.

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

9V = 30mA * R

R = 9V / .030A

R = 300 ohms