Electronic component are classed into
either being Passive devices or Active
devices. A Passive Device is one that
contributes no power gain to a circuit
or system. Examples are Resistors,
Light Bulb, Electrical Heaters. Active
Devices are components that are
capable of generating voltages or
currents. Examples are Batteries and
other Electrical Curent & Voltage
Sources.
By using schematics symbols we can
represent real-life devices.
Resistance -This is a resistance,
measured in units ohms ohms, . Most
often it will be a resistor.
This is a source of emf
(electromotive force) or voltage
source, with a voltage of , measured
in units of volts, V. The most common
source you will see will be a battery.
However, batteries are really not
resistance-free. We can model this
case by putting a 'resistor' in the
circuit which has the same resistance
as the batterys would have.
This is a current source, with a
current of , measured in units of
amperes , A. Current source is ideal
model of electrical power source. The
internal current source resistance is
infinity. We can model real life battery
by putting a 'resistor' in parallel with
curent source.
