## Introduction: Simple Voltage Divider

When building a circuit, there may come a time when you only need a fraction of the voltage that is in the input. Dividing this voltage is simple and requires a few basic components.

You are going to need two resistors of the same value, and a battery. The reason we are using two resistors of the same value is so we will cut the voltage in half. Later I will describe the equation used to calcuate the resistor values needed to achieve a different output such as 3/4 of the input, or 1/8.

I was inspired to write this instructable because I needed 4.5 volts to charge batteries in a circuit, and I had a rechargable 9v battery. I used two 1k ohm resistors to dial this down to the 4.5v needed for my project. It worked perfectly and I still have the circuit now.

As you can see in the picture, I used two 2 ohm resistors, but you can use any value resistors to cut the voltage in half as long as they are equal.

Here is the equation to calculate the Output voltage and the resistor values.

Output Voltage= __r2 __

r2+r1 x Input Voltage

I hope you enjoyed building a voltage dividing circuit, and questions and comments are appreciated so please post them below!

-Doctordv

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## 1 Questions

how much heat does resistors create

P=V*I, and for a resistor, V=I*R, because of Ohm's Law, so the power dissipated (as heat) by a resistor is:

P = V*I = I^2*R = V^2/R

That result is general. So if you have some network with a bunch of resistors in it, you can calculate the power dissipated by each resistor, provided you know the voltage V across (or current I=V/R through) each resistor.

## 2 Comments

this circuit is comonly used to generade a simetric supply; the ground is bad, this have to be were the 4.5v is, and the ground one will be the negative of the batery also is common use a couple of capacitors to keep the volts

but you can use any value resistors to cut the voltage in half as long as they are equal.9V, 4 Ohm; if the battery will supply 2 amps you'll be generating 18 watts of heat in this.

How much current do you get from your charger-divider?

L