EE 47
Lab 1 Report
Insun Amy Jang
Part 2 Controlling the brightness of LEDs

What resistance do you need to limit current to 20 mA?
V = IR (Ohm’s Law)
5V = 0.02 A * R
R = 250(ohms)

Is 220 ohms a maximum or minimum resistance?
220 (ohms) is the minimum resistance because we need to limit current to 20mA and resistance needed for it is 250. By Ohm’s Law, if resistance is lowered, current is increased by the inverse relationship.

What is the resistance range of the potentiometer?
Potentiometer uses similar circuit on the left (from lecture). By changing he location of Vout, we can change range of the potentiometer from 10,000 (ohms) maximum and 0 (ohms) minimum.
Part 3 Basic LED circuit with switch on breadboard

Does it matter what order the components of your circuit are arranged between power and ground? Why or why not?
The order does not matter because if switch is off no current will flow at all, so the order does not matter. If switch is on, the current is decided by the total resistance in the circuit. Since the circuit is serial, there is only one current flow so the order of the components does not matter.
4. Batterypowered LED with switch on breadboard

What is the minimum resistance required for use with the battery?
V = IR (Ohm’s Law)
5V = 220 (Ohms)* I
I = 0.023 A ( maximum current )
V = IR (Ohm’s Law)
9V = 0.023A * R
R = 400(ohms)
Comments (1)
redswood@... said
at 7:38 am on Apr 23, 2011
Great work!
Please keep in mind that LEDs usually have a forward voltage drop when calculating the resistance required to protect the LED from being damaged by too much current. It is okay to ignore that in this lab.
Great to include the circuit of a potentiometer.
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