



SUMMARY

The atom is the smallest part of a matter.

The International System of Units has
seven base units, several derived units
with special names, and many derived units
with compound names.

Basic parts of an atom are the proton,
electron, and neutron.

The presence of charge implies that there
is an electric force field.

The system of units most commonly used
in electrical engineering is the SI.

The work required moving a unit charge
in electric field is a measure of potential
difference or voltage difference. Potential
difference is measured in units of volts.

To define a current, both a value and
a direction must be available.

To define a voltage across an element,
it is necessary to label the terminals
with “+” and ““
signs as well as to provide a value.

Any element is said to supply positive
power if the positive current flows out
of the positive voltage terminal. Any
element absorbs positive power if positive
current flows into the positive voltage
terminal.

Wires are typically assumed to have zero
resistance in circuit analysis.

A ground is a conductor that may be used
as a reference conductor. A reference
conductor may or may not be connected
to Earth.

A branch is a single twoterminal element
in an electric circuit. A node in an electrical
circuit is a point at which two or more
circuit elements are joined together.
A loop is a closed path in a circuit.
The number of branches b, the number of
nodes n, and the number of independent
loops l in a network are related by the
following equation:
 Some
circuits may be solved by combining resistances
in series and/or parallel. A last simple
circuit is obtained and Ohm’s law
may be applied to find voltage and current
in the simplified circuit. The results
are transferred back through the chain
of equivalent circuits. The current and
voltages of interest in the original circuit
can be found.
 Capacitors
store electric field energy. The use of
dielectrics between the plates of the
capacitor increases the charge that can
be stored. When electric displacement
density D is changing in a capacitor it
is analogous to current flow. This current
is called a displacement current.

Inductors are devices that are designed
to store magnetic field energy.

A steady flow of charge is a current measured
in amperes. The relationship between resistance,
voltage, and current is Ohm’s law.








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