Ohm's law is the main basic electrical
law and defines the resistance of a
device to the flow of electrons.
There are three different notations of
Ohm’s law
Unknown Current
Unknown Voltage
Unknown Resistance
(Most people can remember a picture
easier than a mathematical formula.
By knowing any two values you can
figure out the third. Simply put your
finger over the portion of the symbol
you are trying to figure out and you
have your formula).
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.
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.
