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Determine Voltage Drop Across Resistors 2013-03-02

How to calculate voltage drop across series resistors.

Step 1

Determine current of total resistors across the series.

(I = Current/V=Voltage/R(t)=Resistance Total)

I = V / R(t)
I = 9 / (2k + 5k + 10K)
I = .53 mA​

Step 2

Now that we have the Current across the resistors we can calculate the voltage across EACH resistor.

I = Current
Vx = Voltage (x = Current Value across X Resistor)
Rx = Resistor value(x = resistor#)

V = I x Rx

V1 = .53 mA x 2k
V1 = 1.06V

V2 = .53 mA x 5k
V2 = 2.65

V3 = .53 mA x 10k
V3 = 5.3V

V1 + V2 + V3 = 9.01 (voltage is 9V only 9.01 because i rounded up from .529 to .53) At .529 you can see barely a difference:

V1=1.058V
V2=2.645V
V3=5.290V
V Total= 8.993V​

Also If the resistors are all the same value its easier.

To determine the voltage applied by each keypress, you simply add up the voltage drops connected to that key.
So just add them up:

I = V / R(t)
I = 9 / (5k + 5k + 5K)
I = .6 mA

THEN:


V = I x Rx

V1 = .6 mA x 5k
V1 = 3V
so since all Resistors are same value:
V2 = 3V
V3 = 3V

Also To get different values for like switches just use gnd as a start point and the end of each resistor and a end point. This way you get 3 switches from this each having different voltages

SW1 = 3V
SW2 = 6V
SW3 = 9V

So I hope someone can learn something from this.
Author
AtomSoft
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