BASE Definitions

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Definitions

Material copyright 1993 by M. Gore.  All rights reserved.

This is a list of basic electronic terms used in=20
electronics class.

RESISTANCE: The ability of a material to=20
OPPOSE current flow.  All materials have some=20
resistance.  Measured in OHMS for electronics.

CONDUCTORS: The ability of a material to=20
ALLOW current flow.  All materials have some=20
conductivity.  Measured in MHOs.  The opposite=20
of OHMs.

VOLTAGE:  A term used to describe the "force"=20
that causes current to flow in a conductor. =20
Also know as "Electromotive Force (EMF). The=20
symbol is V.

CURRENT: The flow of electrons in a conductor.

AMP:  6.28 x 10 to the 18th power
electrons past a point in one=20
second. That's
  6,280,000,000,000,000,000 electrons !!!
The symbol is I.=20

OHM: The resistance of 1,000 feet of #10 gauge=20
copper wire is 1 ohm.  The unit of resistance.=20
The Symbol is the Greek ohm.

 VOLT: The "pressure" or "Force" to get 1 amp=20
through 1 ohm is 1 volt. The symbol is V.

OHM's LAW:  Voltage is equal to Current times=20
Resistance. V =3D IR

POWER: The amount of "Work" the circuit does. =20
For a resistor it is heat. =20

WATT: The unit of electrical power.  Voltage=20
times Current equals Wattage (if both are in=20
phase with each other). P =3D VI

MAGNETIC FIELD: The invisible magnetic force=20
that surrounds a magnet or is created when a=20
current travels through a wire.

COIL: A simple wrapping of many turns of a wire=20
close together to intensify a magnetic field=20
created when a current passes through the wire. =20
Measured in units of HENRYs. Causes a shift in=20
phase between voltage and current. Stores energy=20
in a magnetic field.  Opposes changes in=20
voltage.  It INCREASES its' IMPEDANCE to voltage=20
changes as frequency goes HIGHER.  It does pass=20
DC.=20
=20


IMPEDANCE: The TOTAL opposition to current=20
flow.  Unlike pure resistance, Impedance takes=20
into account phase relationships between voltage=20
and current, and frequency as well as pure=20
resistance.  Still measured in units of OHMs.=20
The symbol is Z.

CAPACITANCE: A current storage device.  2=20
plates are separated close but away from each=20
other and hold current by electrostatic charge. =20
Opposes a change in current by storing current,=20
and then feeding this stored current out when=20
the supplied current is low.  Blocks DC voltage=20
and current.  Changes its' IMPEDANCE as=20
frequency changes.  IMPEDANCE goes LOWER as=20
frequency INCREASES.  Also causes a phase shift!=20
Measured in units of Farads.

DIODE: Consider this a "one-way current=20
switch".  It allows current flow in one=20
direction only. Must have .6 volts to "turn on".=20

FILTER: A circuit that changes its' impedance=20
with frequency changes.  It allows some=20
frequencies to pass while blocking or reducing=20
others.

TRANSISTOR: A three terminal device (three=20
connections), basic amplifier.  A small change=20
in BASE current causes a large change in=20
COLLECTOR current and voltage.  Two basic types,=20
NPN and PNP.  Almost always silicone.

OP-AMP: A pre-made complex circuit in a simple=20
to use package.  It amplifies the difference=20
between its' two input terminals via a simple=20
mathematical formula: the FEEDBACK impedance=20
divided by the INPUT impedance.

NOISE: Unwanted signals.  Usually refered to as=20
hiss, though includes distortion too.  Lowest=20
noise possible: -128.5 dbm at room temperature.

AMPLIFICATION: When a small change in current=20
and/or voltage causes a larger change in BOTH=20
current and voltage (WATTAGE)in the output.  Can=20
also refer to a large change in just voltage,=20
though an increase in wattage is the correct way=20
to look at this term.

DECIBEL: 1/10 bel.  One BEL is "twice-as-loud"=20
to most people.  A logrymithic relationship=20
between powers (Watts), or voltages.  DBm is=20
decibels measured with 600 ohms at the output=20
device: a audio standard.  DBv is measured into=20
a high-impedance, usually 10,000 ohms.  0dbm =3D=20
.775 volts rms. into 600 ohms.  Most pro audio=20
is set up so the output of a device at 0VU is=20
equal to +4dbm.  Semi-pro gear uses -10dbv. =20


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