# Voltage Dividers

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A Voltage Divider Discussion

If you are in an introductory level electrical engineering course you have probably heard of a voltage divider. Other people that may be interested in learning about voltage dividers include electricians, computer engineers, communication engineers, software engineers, and the technical crowd in general.

I will discuss this concept here without graphs or equations so bare with me. Consider a box that can contain a single source or any other combination of circuit elements. It will be hooked up to a few resistors that are all lined up in parallel and we need to calculate the voltage drop across each of the resistors. In order to properly understand voltage dividers you should understand the basic concepts behind Kirchoff’s Current Law and Kirchoff’s Voltage Law (KVL). Here we will be applying KVL to the resistors that I just spoke about. The law says that the cumulative drop in potential (voltage) across all of the series resistors will sum to the value coming out of our source (box). The voltage potential will start at the value of the source, and drop a certain percentage as each of the resistors elements is encountered.

These voltage drops are calculated using a voltage divider. Consider two resistors in parallel. In order to calculate the voltage dropped across the 1st resistor we need to multiply our voltage source by the value of that resistor and then divide the that value by the total resistance (add both resistors together because they are in series!). The resulting value is the voltage drop across that first resistor. Consequently, that leaves Vsource – Vresistor1 as the value that is left to drop across the second resistor!

Now you can apply this concept to calculate the differences in voltage potentials for just about any circuit and it is on of the most important tools you can learn.