Download Electrical Circuits





Electricity flowing through a substance is
called an electric current.
A circuit is a path through which electricity
flows from a negative terminal to a positive
terminal.
The standard unit for the measure of current
is the ampere, which is often abbreviated
“amp.”
The amount of force per electron flowing
through a substance is called voltage.



A voltage source must be present.
The voltage source must be connected to a
material through which the electric current
can flow.
A circuit must be complete for the electrons
to flow. If the path is broken, the current
stops flowing.


A drawing of an electric
circuit is called a
schematic.
Symbols
◦ Resistor
◦ Battery Source
◦ Switch



The opposition to the flow of electrons is
called resistance. The resistor may also be
called the load and is the part of the circuit
that converts the electrical energy into
another form. (Such as light bulbs).
Resistance is measured in ohms. An ohm is
equivalent to one volt per ampere.
The source of current is also the voltage.
The switch opens and closes the circuit. The
circuit must be closed in order for electricity
to flow.


Series circuit - has
only one path
through which the
electricity can flow.
Parallel circuit - has
multiple paths
through which the
electricity can flow.



Switches are used to
control circuits.
Switches connect or
disconnect all or part
of a circuit.
Switches come in many
forms.
◦
◦
◦
◦
SPST
SPDT
DPST
DPDT


The first and simplest is a Single Pole Single
Throw (SPST). This is a basic on/off switch.
A Single Pole Double Throw (SPDT) is basically
two Single Pole Single Throw switches tied
together so that they function together.


Another type of switch is a Double Pole Single
Throw (DPST). This switch is used for dual
switch control of a single circuit, such as two
switches to control one light in your house.
A fourth type of switch is a Double Pole
Double Throw (DPDT). This is basically two
Double Pole Single Throw switches tied
together so that they function together.


Transistors are small electronic devices that
contain a semiconductor and have at least
three electrical contacts. They were invented
in 1947.
An integrated circuit is a complete circuit on
a piece of semiconductor material. Integrated
circuits were invented in 1958 and led to
even smaller, less-expensive electronics and
eventually to the development of the
microprocessor.