# Voltage divider equation to find voltage into the circuit...

#### callmedave

Joined Jan 11, 2019
5
Hi

I am trying to answer a question where I need to use the general formula for a voltage divider to find the voltage in.

I have rearranged the general formula as follows:

Vout = Vin * Rother / Rtotal

Vin = Vout * Rtotal/ Rother

but i can't come to the correct answer, could someone please tell me if this is due to my rearranging being wrong?

Thanks...

#### Alec_t

Joined Sep 17, 2013
10,456
Welcome to AAC!

• callmedave

#### crutschow

Joined Mar 14, 2008
23,522
Post a circuit diagram and show us which is Rother.

• callmedave

#### WBahn

Joined Mar 31, 2012
24,854
Hi

I am trying to answer a question where I need to use the general formula for a voltage divider to find the voltage in.

I have rearranged the general formula as follows:

Vout = Vin * Rother / Rtotal

Vin = Vout * Rtotal/ Rother

but i can't come to the correct answer, could someone please tell me if this is due to my rearranging being wrong?

Thanks...
I'm guessing that your problem is that you are using the wrong resistor when you say Rother.

An equation is meaningless unless it can be tied to a specific circuit layout. Draw a schematic that clearly shows where Vin in measured, where Vout is measured, what the resistors are and how the individual resistors relate to Rother and Rtotal.

• callmedave

#### dl324

Joined Mar 30, 2015
9,144
I have rearranged the general formula as follows:

Vout = Vin * Rother / Rtotal

Vin = Vout * Rtotal/ Rother

but i can't come to the correct answer, could someone please tell me if this is due to my rearranging being wrong?
It would best for you to learn early that it's best to post a schematic when discussing a circuit; even one that seems (to you) to be simple.

A voltage divider doesn't necessarily need to be for two resistors.

We can tell that your arithmetic is correct, but we have no way of telling whether either equation is correct.

• callmedave

#### callmedave

Joined Jan 11, 2019
5
Welcome to AAC!
Thanks #### BobTPH

Joined Jun 5, 2013
2,055
So, we can see the output voltage on your diagram, and the ? I guess is the input voltage. What do you think Rother and Rtotal are?

Bob

#### dl324

Joined Mar 30, 2015
9,144
This is the circuit I'm working on, it's actually asking for the Thevenin equivalent voltage
Is there supposed to be something in the box with the 560k resistor? Are the circles (on the voltage source) meaningful?

Where's the voltage divider?

#### WBahn

Joined Mar 31, 2012
24,854
This is the circuit I'm working on, it's actually asking for the Thevenin equivalent voltage
Draw you circuit as a meaningful circuit. If the box is being modeled as a Thevenin equivalent, then draw the equivalent circuit, which is a voltage source in series with a resistance.

What is the box on the right that is labeled 53.48 μV? Is that a voltage source? Does it represent a voltmeter? What is the importance of the circle on top being open and the circle on the bottom being closed (filled in)?

In terms of this diagram, what you you saying that Rother and Rtotal are?

You need to communicate your work clearly and unambiguously. Not just here, but to whoever will be grading it, too.