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ELEMENTS OF ELECTRICAL INSTALLATIONS
SWITCHES
QUESTION: What is an electrical switch? What types of switches do you know?
A switch is an electrical component that can break an electrical circuit, interrupting the current
or diverting it from one conductor to another. The mechanism of a switch may be operated:
-
directly by a human operator to control a circuit (for example, a light switch or a
keyboard button), known as HAND SWITCHES,
by a moving object such as a door-operated switch, known as LIMIT SWITCHES,
by some sensing element for pressure, temperature or flow, knows as PROCESS
SWITCHES.
TYPES OF SWITCHES

One way to categorize switches is by the movement a person uses to open or close the
contacts. There are many different switch designs. The most common hand switches are:
A. Pushbutton switch is a switch that has a knob that you push to open or close the
contacts. Each time you push the switch, the contacts alternate between opened and
closed.
B. Joystick switches are actuated by a lever free to move in more than one axis of motion.
C. Toggle switches are actuated by a lever angled in one of two or more positions.
D. Selector switches are actuated with a rotary knob or lever of some sort to select one of
two or more positions.
QUESTION: What do the switch symbols mean – SPST, SPDT, DPST, DPDT?
 Two important factors that determine what types of connections a switch makes are:

Poles: A switch pole refers to the number of separate circuits that the switch controls. A
single-pole switch controls just one circuit. A double-pole switch controls two separate
circuits.
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(A double-pole switch is like two separate single-pole switches that are mechanically
operated by the same lever, knob, or button.)


Throw: The number of throws indicates how many different output connections each
switch pole can connect its input to.
Switches can be divided into categories:
single pole
(SPST)
It turns a light or a device on and off from a single
location. This switch has two terminals and is wired
to the hot (black) wire. The switch may or may not
come with a ground terminal (green screw).
double
pole
(DPST)
This switch also has "on" and "off" markings and
functions similar to a single pole switch in that it turns
something on and off from one location.
three-way
(SPDT)
It switch is always used in pairs and allows you to turn
a light or receptacle on and off from two different
locations.
four-way
(DPDT)
It is used in between two three-way switches to
control an outlet or light fixture from three different
locations.
GANGS AND WALL PLATES
Each side-by-side element in an electrical box is called a gang. For example, a 3-gang switch
plate would have openings for three side-by-side switches.
single outlet plate
duplex outlet plate
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RECEPTACLES

Ćwiczenie.
Na podstawie poniższego fragmentu rozszyfruj wytłuszczone zwroty:
“ I have a dead outlet in my kitchen. The problem started when I installed my washing machine.
The plug has a grounding pin, but the outlet does not have a grounding slot. I also wanted to
plug in a lamp, but the outlet is only a single outlet. I used a cheater plug to make a duplex
outlet with a grounding slot. One more question: Can I use a three-pronged plug with a twoslot outlet?“
 Grounding pin –
 Grounding slot –
 Single outlet –
 Duplex outlet –
 Cheater plug –
 Three-slot plug –
 Two-slot outlet –
FUSES AND CIRCUIT BREAKERS
QUESTION: How does a fuse work? How is it built?
QUESTION: How does a circuit breaker work? How is it built?
QUESTION: How often do you replace a fuse and a circuit breaker?
Fuse
A fuse breaks the circuit if a fault in an appliance causes too much current flow. This
protects the wiring and the appliance if something goes wrong. A fuse is made up of a piece of
metal that melts when overheated. If the current going through the fuse is too great, the wire
heats up until it melts and breaks the circuit. The problem with fuses is they only work once.
You must replace the fuse after it melts.
Circuit breaker
A circuit breaker does the same job as the fuse, but works in a different way. It has an
internal switch mechanism that is tripped by an excessive current. The basic circuit breaker
consists of a simple switch, connected to either a bimetallic strip or an electromagnet. The hot
wire in the circuit connects to the two ends of the switch. When the switch is flipped to the on
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position, electricity can flow from the bottom terminal, through the electromagnet, up to the
moving contact and out to the upper terminal. When the current is too big, the electromagnet
disconnects the contacts and the current stops flowing. A circuit breaker does not need to be
replaced every time it is used – it can be simply reset.

Ćwiczenie.
Przeczytaj tekst i uzupełnij podane pod tekstem zdania. Podaj znaczenie pogrubionych
wyrazów.
ZYX Electrical Supply
Electrical overload can result from various factors, such as a short circuit from a ground fault.
Your fuses or circuit breakers protect your system from these excessive currents. If you need a new
fuse or circuit breaker for your ZYX panel, use your handy replacement guide.
ZYX no longer makes panels with fuses, but we carry replacement fuses for our older models. If
your fuse is encased in a tube with metal end caps, check out our cartridge fuses. If you can
unscrew the fuse from its socket, you need a plug fuse. All blown fuses must be replaced since
they cannot be reused.
Newer ZYX panels have circuit breakers instead of fuses. Unlike fuses, circuit breakers do not need
replacement every time they are tripped. But broken or worn out breakers occasionally require
replacement. Our breaker diagrams will help you determine if you need a single pole or double
pole breaker.
1.
An electrical surge might trigger the circuit breaker.
_ri_
2.
Make sure to get a new type of fuse that screws into a socket.
3.
The metal strip in my fuse has melted. I think this is a _ l _ _ _ fuse.
4.
If you want it to supply 240-volt power, you need a _ o _ _ _ e
5.
A c _ _ _ _ _ d _ _ fuse is usually made of glass and metal.
6.
The power went out because of an electrical o _ _ _ _ o _ _.
7.
The short circuit was caused by a _ _ o _ _ _
f _ _ _ t.
_l_g f___
_o_e
b _ _ _ - e _.
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four-way
switch
(DPDT)
single pole
switch
(SPST)
double
pole switch
(DPST)
three-way
switch
(SPDT)
It switch is always used in pairs and allows you to turn a
light or receptacle on and off from two different
locations.
It is used in between two three-way switches to control
an outlet or light fixture from three different locations.
This switch also has "on" and "off" markings and
functions similar to a single pole switch in that it turns
something on and off from one location.
It turns a light or a device on and off from a single
location. This switch has two terminals and is wired to
the hot (black) wire. The switch may or may not come
with a ground terminal (green screw).
JOYSTICK SWITCH
TOGGLE SWITCH
PUSHBUTTON SWITCH
SELECTOR SWITCH