Subject: BASE Definitions
From: "Saved by Windows Internet Explorer 8"
Date: Wed, 22 Sep 2010 16:03:57 -0700

Definitions

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

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

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

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

VOLTAGE: A term used to describe the "force"
that causes current to flow in a conductor.
Also know as "Electromotive Force (EMF). The
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
second. That's
6,280,000,000,000,000,000 electrons !!!
The symbol is I.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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