Household Electrical Basics
Electric Basics                                                        Click here for a printer friendly version
Most of the receptacles in a typical house are wired for 120 volt AC electrical power.  The power/current flows between the 'hot' and
'neutral' wires.  To reduce the risk of surges and unstable voltage, the neutral wire is connected to earth ground at the main
electrical panel.  Typically electrical shocks happen when a persons body is 'grounded' (the worst case is standing barefoot on the
damp ground/soil or concrete) and they come in contact with the 'hot' side of the electrical power.  This can happen when a metal
cased appliance (e.g. a washing machine) has a defect which allows the case to become energized (e.g. the insulation on the
power cord is damaged) and a person touches the appliance.  It takes very little electrical current to cause death or serious injury.  
Connecting the metal case of the appliance to ground will greatly reduce the risk of electrical shocks.
Brady Home
Inspection
Eureka, CA

707 444-9922
3-Prong Receptacle
3-Prong Plug
GFCI Receptacle
3-Prong Receptacles

3-prong receptacles are the standard type
in use today.  The smaller slot is designed
to be connected to the 'hot'  (or 'live') side of
the house wiring.  The longer slot is
designed to be connected to the 'neutral'
side of the house wiring.  The semi-round
hole is for the ground connection (the
grounding conductor).
 3-Prong Plug

Appliances which have a 3-prong plug must
be plugged into a properly wired receptacle to
provide the intended protection against
electrical shock and damage to sensitive
electronic equipment.  Typically these are
supplied with metal cased appliances or
appliances that are used with or near water.  
They are also used on equipment with
sensitive electronics and surge protectors.
 GFCI Receptacle

Used to provide additional protection
against dangerous electrical shocks.  
See dedicated GFCI protection page.
2-prong receptacle
2-Prong Polarized Plug
3-Prong to 2-Prong Adapter
2-Prong Receptacles

2-prong receptacles were widely used until
the mid 1960's.  Until then, most of the
wiring in a typical house did not include a
grounding conductor.   The narrow slot is
designed to be connected to the hot side of
the electrical power.  Most household
appliances have 2-prong plugs and are not
affected by the lack of the ground
connection.
 2-Prong Polarized Plug

There are two types of 2-prong plugs,
polarized & non-polarized.  Polarized plugs
are used on some appliances to ensure that
the hot side of the electrical power is
connected correctly to reduce the risk of
electrical shock and/or damage to the
appliance.  A non-polarized plug can be
plugged in either way.
 3-Prong to 2-Prong Adapter

An adapter is designed to allow a
3-prong plug to be connected to a
2-prong receptacle.  These are typically
misused due to the fact that the green
tab is usually not connected to ground.  
To provide the intended protection the
green tab must be connected to ground.
Typical Defects Noted During Inspections:

  • Open Ground - A 3-prong receptacle where the ground connection is not attached.  This typically occurs on a house where
    the older wiring does not have a ground conductor.  Without the ground connection, an appliance with a 3-prong plug will not
    have the intended protection.  A surge protector requires the ground connection to protect sensitive equipment from
    spikes/surges.

  • Reverse Polarity - The hot and neutral connections are reversed at the receptacle.  An appliance with a 3-prong plug or a
    polarized 2-prong plug is designed to have the hot side connected properly.  Because of this, a reverse polarity condition
    should be corrected.