I have been thinking about an electrical thread for a long time. The biggest problem I see with the vehicles I work on is people wiring up stuff from scratch and not knowing what they are doing. So this is a post to inform about the basics of any automotive wiring circuit.
Voltage- Can be defined as an electrical pressure and is the electromotive force (EMF) that causes the movement of electrons in a conductor. Voltage is the force of attraction between the positive and negative charges.
Current- can be defined as the rate (INTENSITY) of electron flow and is measured in amperes. Current is a measure of the electrons passing any given point in the circuit in one second. Current will increase as voltage increases - provided circuit resistance remains constant.
Resistance- is the opposition to current flow (ie your electrical load, a light for example) resistance is measured in OHMs. Resistance controls the amount of current flow.
Voltage always drops as current flows through the resistance.
An increase in resistance causes a decrease in current.
All resistance change the electrical energy into heat energy to some extent.
Voltage drop- occurs when current flows through a load (ie like light bulb or a resistor) voltage drop is the amount of voltage that is used up by the component. After a resistance, the voltage is lower than it was before the component.
Kirchhoff's law- basically states that the sum of the voltage drops in an electrical circuit will always equal source voltage. ie battery voltage. In other words, all of the source's voltage is used by the circuit. To find voltage drop, we multiply the current by the resistance. This is the key to how nearly all pcm's, and other controllers and sensors work in your pimped out ride.
Ohm's Law- is the key to understanding how electrical circuits work!!!!!!!!!!
The law states that it takes one volt of electrical pressure (EMF) to push one ampere of electrical current through one ohm of resistance. Mathematically expressed as 1 VOLT= 1 AMPERE X 1 OHM This formula is most often expressed as E = I X R
E is for volts, I is amps and R is for resistance.
Example-
E
-----
I | R
So, if we have 2 amps of current flowing through 6 ohms of resistance we would then have 12 volts. Or if we knew that our battery voltage was 12 volts and we also knew that our lamp or motor or winch had 6 ohms of resistance we would then know that we would have 2 amps of current flowing through the circuit and we would be able to get by with a 5 amp fuse.
Series Circuit- consists of one or more resistors (or loads) with only one path for current to flow. Think of it like the old fashion Christmas tree lights that if one bulb burnt out they ALL WENT OUT!
in a series circuit the total resistance (OHMS) is the total of all resistances ( LOADS IN A CIRCUIT) three light bulbs with 1 ohm of resistance each for a total of 3 ohms.
the current (AMPS) will be the same at any point in the circuit.
the voltage drop across each resistance will be different if the resistance values are different.
the total of all voltage drops must equal source voltage.
Parallel Circuit- basically allows current to flow through multiple paths. The new Christmas tree lights will not all burn out if one bulb does.
The voltage applied to each leg of the circuit is the same.
The voltage drop across each leg of the circuit will be the same, unless multiple loads are in that leg.
The total resistance in a parallel circuit is always less than the lowest individual resistance, because current has more than one path to follow. Calculating total resistance in a parallel circuit becomes complicated!!!! AND will not be discussed at this time.
