impedance

[Don]

Hi all,

I think I can safely say a sound board is *none* of the below. *grin*

impedance (from http://www.oup.co.uk/isbn/1467-3894/ )

 
The total opposition to current flow in an electrical circuit,
measured in ohms (Ω). In a direct-current circuit the
impedance (symbol Z) is equivalent to the resistance (R),
but in an alternating-current circuit it is the ratio of the
alternating voltage to alternating current, and is composed
of the combined resistance, inductive reactance
(inductance), and capacitive reactance (capacitance),
according to the equation: I2 = R2 + X2, 

where X is the reactance.

reactance 

 
The opposition, measured in ohms (Ω), of a reactor
(a capacitor or an inductor) to alternating current. Unlike
resistance (see resistor), reactance varies with the
frequency of the alternating current; the reactance of an
inductor increases with increasing frequency, while that of
a capacitor decreases. (See also impedance) 

capacitance and capacitors 

 
Capacitance is the property of an electrical system of
conductors and insulators that enables it to store charge.
The greater the potential, the greater the amount of charge
that can be stored. For a charge of magnitude Q and a
potential difference of V, the ratio Q/V is the capacitance,
which is a constant for that capacitor, measured in farads.
The farad is a very large unit: in practice, values range
between 10-12 and 10-6 farad. 

A typical capacitor consists of two parallel conductors
consisting of metal plates or electrodes separated by an
insulator or dielectric. A capacitor presents an extremely
high resistance to a direct current (d.c.): no current will
flow in a d.c. circuit containing a capacitor. However,
alternating current (a.c.) is allowed to pass much more
easily, and the higher the frequency of the a.c. signal, the
less opposition the capacitor presents. Because of this
ability to separate a.c. and d.c. signals, capacitors are
frequently employed in both filters and power supplies.
Several types of capacitor exist. Ceramic capacitors are
used in radio-frequency circuits, while capacitors made
from polyester and polycarbonate plastics have general
application.

Source: ope 

 
                                                 
Regards,
Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T.

Tuner for the Saskatchewan Centre of the Arts

drose@dlcwest.com
http://donrose.htmlplanet.com/

3004 Grant Rd.
REGINA, SK
S4S 5G7
306-352-3620 or 1-888-29t-uner