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Chassis Electrical and Ignition / Re: Basics: The Importance of Vehicle Ground
« Last post by bd on Today at 12:19:49 pm »GLOSSARY OF SYMBOLS AND TERMS
> — "greater than" math symbol used to compare relative values. The arrowhead always points to the lesser value: a > b, means value "a" is greater than value "b".
≥ — "equal to or greater than" math symbol used to compare relative values. The arrowhead always points to the lesser value: a ≥ b, means value "a" is equal to, or is greater than value "b".
< — "less than" math symbol used to compare relative values. The arrowhead always points to the lesser value: a < b, means value "a" is less than value "b".
<< and <<< — "much less than" math symbols used to compare relative values. Generally limited to three, the greater the number of arrowheads (<) in the series, the greater the separation between the compared values.
Ag — chemical symbol for silver (from Latin: argentum)
B- — effectively, the negative terminal of the battery or power source. In a negative ground electrical system, B- is defined as possessing zero electrical energy.
"____" bus (also, buss) — a primary current pathway or circuit channel emanating from (the power bus or supply bus) or toward (the ground bus or return bus) a power source and leading to or returning from a circuit, to which other conductors or circuit channels are connected and depend. The physical conductor, sometimes of a heavier gauge, that is common to and shared by one or more discrete circuits. A bus(s) is a shared current path that is common to both the power source and its connected circuit or circuits.
circuit — the complete path of an electric current. A circuit, to be complete, must connect to one terminal of a power source, run through a load, and return to the opposite terminal of that same power source in a continuous, uninterrupted, conductive loop.
common — a current path or electrical connection that is shared by multiple circuits (e.g., common positive; common negative). Typically, however, by consensus and unless otherwise noted, 'common' refers to the ground bus or the point of ground connection between an electrical device and its power source.
current — the rate of coordinated migration or movement of individual electric charges. Expressed in amperes, current is the net electric charge per second flowing past a defined, stationary reference point. One ampere equals ~6.24 x 1018 electric charges per second (one Coulomb per second) of current flow. Current flow is forced by differences in potential, naturally flowing from regions of high electric charge (high potential) to regions of low electric charge (low potential) to establish a uniform charge across all regions. Current is never consumed by a circuit or any of its components. Whatever quantity of charge leaves a power source to enter a circuit must simultaneously exit that circuit and return to that same power source. That is to say, the current flowing into any circuit or component precisely equals the current flowing through and out of that same circuit or component — current IN equals current OUT. Conversely, current OUT equals current IN.
electric charge — a quantifiable property of certain elementary atomic particles (i.e., electrons and protons) that causes them to exert forces on one another across a distance. By convention, electrons have a negative charge and protons have a positive charge. Electric charge is the collective or net effect of the negative and positive charges at a specified location. In practical application, electric charge is caused by the surplus (excess) or scarcity (absence) of electrons (e-) with respect to what is normal for a given substance.
floating ground — an electrically isolated “ground” possessing a non-zero voltage relative to the general system ground (or zero voltage reference bus). Floating grounds generally result from poor electrical connections within the ground circuit, and are universally undesirable.
ground (earth) — systematically chosen for convenience, ground is the effective base or reference potential in an electric circuit to which all other potentials are measured or otherwise quantified and compared, and which is defined as and assumed to be zero. The zero reference terminal of a power source. The zero-voltage reference bus. Commonly, the terminal of the power source that is conductively connected to the chassis or greater supporting frame of a device. The current return-flow conductor or circuit channel, or system of conductors or circuit channels, that connects one or more loads to the zero reference terminal of the power source. All potential differences within a given circuit or interconnected network of circuits are quantified (measured) with respect to ground. Ground (earth) is considered to possess sufficient relative mass to sink or null (absorb and effectively disburse or dispense) any transient or spurious electric charge to zero.
HVAC — Heating, Ventilation, Air-Conditioning system
load — two distinct definitions within the context of electrical circuits: 1) although it can be any component that consumes electrical power, "load" as an object, typically refers to the specific appliance a circuit is designed to control. A load is labeled as such because of the demand it places upon the power source. In any given complete circuit, the resistance of the load is inversely proportional to the current flowing through that load: the lesser a load’s resistance, the greater its current demand. Conversely, the greater a load's resistance, the lesser its current demand. By design, the greatest resistance in any given complete circuit is the load. 2) as a quantity, "load" is the amount of current burden that an appliance imposes on its power source. Current load is synonymous with current flow; the greater the (current) load, the greater the current flow. Thus, a large load implies high current demand; a small load implies low current demand. When "load" refers to an object, it generally refers to the specific appliance burdening the power source. When "load" refers to a quantity, it refers to the current demanded from the power source by the appliance. Example: "The load [e.g., an LED fog lamp] imposed a 5-amp load [i.e., current demand] on the battery." The key to understanding and avoiding ambiguity is recognizing the context of usage and knowing the multiple meanings of ‘load.’
Pb — chemical symbol for lead (from Latin: plumbum)
potential — (aka, electric potential) the work expended to accumulate and maintain an electric charge at a specified location
potential difference — the difference in potential between two distinct and separate points
resistance — expressed in ohms and dependent on the geometric length and cross-sectional area of a wire or cable, resistance is the opposition to simple direct current (DC) flow. Every conductor and electrical component possesses some amount of resistance. Resistance is always cumulative. As resistance increases in a circuit, current flow decreases. In a fixed-voltage system, resistance controls the current flow: the greater the resistance, the less the current flow.
resistivity — expressed in ohm meters and dependent on temperature, a fundamental material property that quantifies how strongly a material opposes the flow of electric current regardless of its volume or shape.
Sn — chemical symbol for tin (from Latin: stannum)
sub-circuit — one of two or more circuits that share direct or indirect connections to the power bus and ground bus of a power source
terminal — a point of electrical connection for the effluence or return of current
voltage — the quantification of potential expressed in volts (or joules per unit charge). Voltage is the difference in electric charge that exists between two discrete points that are separated by a distance greater than zero and represents the amount of force available to equalize the electric charge between those discrete points. Within an electric circuit, voltage is the potential, measured relative to ground, that is available to force the movement of electric charge or current.
voltage drop — expressed in volts, the work performed in forcing the migration of electric charge. Within an operating circuit, the amount of voltage necessary and consumed in forcing current flow through a resistance. Current must flow for the voltage to drop. When no current is flowing, the measured voltage is limited to two possible states: either the power source voltage or zero. The relative decrease in voltage between two discrete points that are separated by a resistance while current is flowing between those two points through that resistance. Voltage drop is the charge differential created across every circuit and circuit component that exhibits resistance while current is flowing through that circuit and its components. The source voltage is distributed proportionally across every resistance in an operating circuit, such that all of the applied voltage is consumed. That is, some portion of the source voltage is consumed by each resistance in the circuit, such that 100% of the voltage is used. Voltage is always consumed, decreasing to zero, in the process of forcing current flow.