Determine Voltage Drop Across Resistors

I learned this from http://www.bcae1.com/resistrs.htm
I know some true nooBs would like this info so i decided to post it again

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.

From: I²R
https://www.electro-tech-online.com/threads/multiplex-switches.36930/


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

Click to expand...

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.

This Voltage Drop Across Resistors article is now in the Theory section.

Thank for posting this, Im quite beside myself with being dejected for being to stupid .
Im trying to figure out how to figure the voltage drop over to resistors.
The example Im using is a DC circuit
V=25
R1=3.3
R2=2.5
I =6.3
I told ( according to an quiz) that the voltage drop @ R1 is described as 21V
and R2 as 14
I have know idea how to come up with those values.
Any insight would be greatly appreciated.

It is wrong.......

FITNAH said:

Thank for posting this, Im quite beside myself with being dejected for being to stupid .
Im trying to figure out how to figure the voltage drop over to resistors.
The example Im using is a DC circuit
V=25
R1=3.3
R2=2.5
I =6.3
I told ( according to an quiz) that the voltage drop @ R1 is described as 21V
and R2 as 14
I have know idea how to come up with those values.
Any insight would be greatly appreciated.

Click to expand...

Ohms law says that E/R=I, so I should be 4.31A
So if E= IxR what do you get?

34.65a.
I get 6.36 for I ,dividing the combined resistance into V.
which then in turn gives me a voltage drop of 20.79 =R1 and 15.75 =R2
which also doesn't add up to 35 the original answer.

FITNAH said:

34.65a.
I get 6.36 for I ,dividing the combined resistance into V.
which then in turn gives me a voltage drop of 20.79 =R1 and 15.75 =R2
which also doesn't add up to 35 the original answer.

Click to expand...

How can 25v/5.8 ohm be anything but 4.31A?

Sorry typo, the model I have here is V =35
4.54 is of course correct, sorry about being sloppy.

I already feel like quit the idiot over not knowing how to find this answer and now flubbing the question hasn't helped,
In any case their must be a formula for finding the voltage drop over two or more resistors of different values

FITNAH said:

I already feel like quit the idiot over not knowing how to find this answer and now flubbing the question hasn't helped,
In any case their must be a formula for finding the voltage drop over two or more resistors of different values

Click to expand...

Ohms law and a little thought!.

Thanks, the voltage drop across the resistors must add up to the voltage correct?

For a start draw the circuit and post it here!.

Oh this is to embarrassing,
I glad it happened here before any classes started I haven't been in school for 20 years.
I went back to find the problem and to my relief I found, Im still an idiot, just not the kind I was beginning to believe I was.
I had mistake when I copied the problem off the internet, then went about trying to get the right answer with the wrong numbers.

This has been a very good lesson for me.

Take your time check what you are doing and pay attention .
R2 is 2.2
not 2.5.

Copying errors cause a lot of problems. Make sure you read over the entire problem on tests, too. That caused me a lot of headaches.

Thanks I'm now in class and doing well.

Im glad to see this was helpful.