# Circuit Lab/Solving Resistor Circuits

*This is a tutorial page for the event Circuit Lab about solving resistor circuits*

The total voltage in the circuit stays the same. Only the voltage used by individual components changes. Here's an example using the formulas for series circuits:

## Series Circuits Formulas

Ohm's Law (stated 3 different ways):

[math]E = I \times R[/math]

[math]I = E/R[/math]

[math]R = E/I[/math]

[math]E_{total} = E_{R_1} + E_{R_2}.... + E_{R_n}[/math]

[math]R_{total} = R_1 + R_2.... + R_n[/math]

[math]I_{total} = I_{R_1} = I_{R_2}.... = I_{R_n}[/math]

### Circuit 1

To learn everything about this circuit we can use a chart. Start by entering what we know:

Using the formula: R(total) = R1 + R2.... + Rn we can find the total resistance:

We can now use Ohm's Law in the form of I = E/R to find the total current in the circuit

From the formula: I(total) = I(R1) = I(R2).... = I(Rn) we can now determine the current in both resistors:

Lastly, we can use Ohm's Law E = I x R to find the voltage used by each of the resistors

Note: Power (P) is measured in Watts (W). The formula is: P = I x E

### Circuit 2

In Circuit 2 resistor #1 is increased to 9 ohms with all other parameters remaining the same. Calculate the values for this circuit just as in Circuit 1. Results are:

Note: The voltage used by resistor 1 increased and the voltage used by #2, the current and total power decreased.