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ee 47 lab report 1

Page history last edited by Jomar 13 years ago

Lab 1

Jomar Sevilla

a. What resistance do you need to limit current to 20 mA?

Using Ohm’s Law, we set up R=V/I to find the Resistance that will limit current to 0.02Amps

However we must take into effect the voltage drop or forward voltage necessary to light up the LED. From the red LED datasheet, we know the voltage drop is around 2 Volts.

R = (5-2)Volts / 0.02Amps = 150 ohms; Therefore 150 Ohms will limit current to 20 mA.

b. Is 220 ohms a maximum or minimum resistance?

220 ohms is a minimum resistance.

c. What is the resistance range of the potentiometer?

The blue potentiometer with three prongs has an ideal rating of resistance range of 0Ohm to 10kOhms. Measuring with a multimeter, the measured resistance is 0.5Ohms to 9.9kOhms.

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

The order of all the components in this circuit does not matter because everything is in a series. The order of the resistors, potentiometer, switch, or LED does not matter because all the resistance in a series simply add up.

a. What is the minimum resistance required for use with the battery?

Using R = (V-Vdrop)/I

R = (9-2Volts)/ 0.02 Amps = 350 Ohms. To limit the current to 20mA, the minimum resistance needed is a 350 Ohm resistor.

Comments (1)

Excellent work!
Nice to consider the LED forward voltage drop in calculating the resistor required for protecting the LED from being damaged by too much current.
Great to measure the actual resistance of the potentiometer using a multimeter, instead of just looking at the datasheet or label.

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