We are trying to keep our discussions in some kind of order so that they make sense. When there is so much to talk about, I get excited and want to throw all sorts of new ideas at you. Then I realize that would discourage some and I have to hold myself back. I want to spend more time discussing Ohm’s law because it is extremely important to understand this law when we talk about electrical systems.
However, we are going to take a short break this week to introduce yet one more vocabulary term: Power. What is “power”? Wikipedia, the online encyclopedia, defines power as “the amount of work done or energy transferred per unit of time”. The important word here is “work”. There are many forms of work and the one we want to consider here is the electrical form. Most electrical work shows up as heat, and you can generally tell if electrical work is being done if there is heat present.
(I want to get a little off topic here to talk about “work” a little more. More specifically, about conversion of energy. In physics, there is a “law of conservation of energy”, which tells us that we cannot destroy energy, we can only convert it into another form. For instance, when you are driving your RV down the highway, you are converting the energy in the fuel in the tank into mechanical energy to propel the RV down the road. Something most folks don’t think about is that when you turn on your windshield wipers, or your headlights, you are also using energy. That energy has to come from someplace, and so, when you turn on your accessories, you actually reduce your fuel mileage by a slight amount.
Anyway, when you do these things, you accomplish “work”, and this is done by generating power. Power in an electrical system is a “product”, like the product we all learned in 7th grade math class. It is the product of multiplying volts time amps, and is another form of Ohm’s law as shown below, with “P” representing power:
P=E*I
So, if we know the volts in an electrical system, and the amps, we can multiply them together and find the amount of power being used in the electrical system. A simple example would be if you have a 12v system running a lamp with 1 amp of current flowing, the lightbulb would produce, or use 12 watts of power. Turn that around a little and you can find what amperage will flow in a circuit if you know the lightbulb wattage rating and the circuit voltage. This can be very useful when working on an electrical system.