Basic Electronic Formula
If you remember our basic idea of a tank filled with water, then it shouldn't be hard for you to comprehend how the different aspects of electronics work together to form a circuit. Consider the basic water tank with a valve added to it's base. As we turn the valve the water begins to flow. In the path of the water we have installed a simple turbine which begins to spin. As the valve is opened more, the turbine spins faster.

If we open the valve to it's full position, the water will drain out faster than if the valve were only opened half way. This is the concept of how a resistor works... it controls the flow of the electrons to produce the desired effect, prevent damage to components, or keep the power source from working harder than necessary. Below you will see the concept model we have just described.
Water Tank Concept Model Basic Electronic Formula
Water Level / Pressure
VOLTAGE = V

Flow Control Valve
RESISTANCE = R

Water Speed / Flow
CURRENT = I

Work By Turbine
POWER = P
Once you have the basic model in your mind, you can begin to see how the components effect each other. When you have a good grasp of these four basic formulae and how they interact, you will be able to calculate most of your circuit needs. We will refer to this page often as we explore electronics and circuit components.
Definitions
Formula Value Measurement Description
V = I * R VOLTAGE VOLTS Voltage represents the amount of free electrons available as an energy source. As the circuit operates the battery is drained, and the voltage goes down
R = V / I RESISTANCE OHMS Resistance is the friction that the electrons have to fight to complete the circuit. As the resistance of a component is increased, the flow of electrons or current goes down.
I = V / R CURRENT AMPS Current is the speed at which electrons flow through a circuit. The stronger the current, the more heat is generated, and the faster the battery is drained.
P = V * I
or
P = I2 * R		 POWER WATTS Wattage depends on the efficiency of the components. As a motor works harder it's current increases which causes the wattage to also increase. Always design your circuit to be slightly higher than the wattage you anticipate to prevent failures.