 One of the most common circuit fragments is what we call a voltage divider or a potential divider. A voltage divider is simply a circuit which produces a predictable fraction of the original or input voltage as the output voltage. So it converts an input voltage to a different output voltage. Here's a diagram of the simplest possible voltage divider. So it consists of an original voltage source, then two resistors, R1 and R2. The load is then placed in parallel with R2, as we can see in this bill of the circuit here. So this load, which is labeled by V out, so this will cause a predictable voltage across the load, labeled here with V out. I'm going to call this section of the circuit highlighted in yellow the junction. So we'll call the input voltage V in and the voltage across the load, the output voltage V out. Now I'm going to show you how V out can be calculated if you know V in, R1 and R2. Using our formula for resistors in parallel, we get the total resistance across the junction is 1 over the resistance of the junction is equal to 1 over R2 plus 1 over the resistance of the load, whatever the resistance of this load here is. So to calculate the voltage across this junction, we assume that the load has an extremely high resistance. This means that 1 on R load is very small, we just say approximately zero. Therefore, 1 over the resistance of the junction is equal to 1 over resistance 2. So therefore, the resistance of the junction is equal to resistance of this resistor 2. Therefore, Rj is equal to R2. Now since R1 and the junction are in series, the total resistance of the circuit is given by R1 plus R2. So then we can calculate the current through R1 and R2 using Ohm's law. So the current equals the voltage in divided by the total resistance which is equal to V in divided by R1 plus R2. Now that we know the current flowing through the circuit, we can find the voltage across R2. The voltage across R2 is going to be equal to the current flowing through it times the resistance of R2 which is equal to R2 times V in divided by R1 plus R2. But using the loop rule, we know that the voltage across R2 must be the same as the voltage across the load V out. So therefore, the voltage V out is going to be equal to R2 times V in divided by R1 plus R2. So this is the formula for the output of a voltage divided circuit. Although the derivation involved many steps and may have been a bit confusing, no new ideas were presented. So I recommend that you take some time to look over it and check that you understand what was assumed in each step and what equations were used in each step.