Charge • Amps • Volts • Ohms
Charge is a fundamental property of some sub-atomic
particles of matter. For example, electrons have one dose of negative charge, protons
one dose of positive charge. Opposite charges electromagnetically attract
while same-signed charges repel.
Electrons are tiny, fast-moving and abundant. Electromagnetic
causes them to gather
around more massive, proton-laden nucleuses. One nucleus and its
cloud of electrons is called an "atom".
Atoms, in turn, bond electromagnetically to other atoms, forming even more stable electrical landscapes or
"fields". Tennis balls bounce,
stand, and aspirin
thins the blood thanks to electromagnetic fields.
CONDUCTORS, CURRENT, and INSULATORS
Unpaired electrons on the outer
fringes of atoms are weakly bound to their nuclei and can flow en masse in materials called
"conductors". Metals like tin, copper, and gold have lots of free electrons
and are good conductors.
A flow of charged particles is called an electric "current".
The unit of measure for current is the "ampere" (or "amp" for short), abbreviated "A"
(capital A because Ampère was a person).
Materials having tightly bound electrons are called "insulators".
These materials, like wood, rubber and glass, are poor conductors of
electric current. They're
like dams or steep shorelines to the flow of current.
RESISTORS and VOLTAGE
"Resistors" are engineered from materials like carbon.
They impede electric
current in a partial, controllable way. These materials have no pool
of free electrons that can be shoved downstream domino-style. Some
electrons will drift through the atomic lattice but most
are stopped by it, producing more
heat than electric current.
Electrical pressure rises across a resistor like water pressure rises across a clogged drain. The pressure
difference between one end of the resistor and the other is called the "voltage"
across the resistor. The unit of measure for voltage is the
"volt", abbreviated "V"
(capital V because Volta was a person).
If we divide the voltage across a resistor by the current through it
[volts/amps], we get a number that's constant for that resistor. In
other words, if we double the voltage across it, the current through it
will also double.
This constant is called the "resistance" of the resistor.
Its unit of measure is the "ohm", abbreviated "Ω" (capital
Omega because Ohm was a person).
The math symbols for voltage, current, and resistance are "
R". The equation
R = V/I is called Ohm's Law even though it was
discovered a century before Ohm popularized it.
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