1. ysPlywood is a manufactured wood panel from the family of manufactured boards (such as
medium-density fibreboard (MDF), particle board (chipboard), etc.) made from thin sheets of
wood veneer. Plywood layers (called veneers or plies) are glued together, with adjacent plies
having their wood grain rotated relative to adjacent layers up to 90 degrees.
All plywoods bind resin and wood fiber sheets (cellulose cells are long, strong and thin) to form
a composite material. This alternation of the grain is called cross-graining and has several
important benefits: it reduces the tendency of wood to split when nailed at the edges; it reduces
expansion and shrinkage, providing improved dimensional stability; and it makes the strength of
the panel consistent across all directions. There are usually an odd number of plies, so that the
sheet is balanced—this reduces warping. Because plywood is bonded with grains running against
one another and with an odd number of composite parts, it is very hard to bend it perpendicular
to the grain direction of the surface ply.
Smaller thinner plywoods and lower quality plywoods (see Average-quality plywood photo
below and right) may only have their plies (layers) arranged at right angles to each other, though
many better quality plywood products will by design have five plies in steps of 45 degrees (0, 45,
90, 135, and 180 degrees), giving strength in multiple axis. The highest quality specialty
plywoods often have plies at 30 degrees (0, 30, 60, 90, 120, 150, and 180 degrees) in seven
layers, or have nine layers with two layers of 45 and 135 degrees in the sandwich. The smaller
the step rotations the harder it is to manufacture, increasing manufacturing costs and
consequently retail price
A typical plywood panel has face veneers of a higher grade than the core veneers. The principal
function of the core layers is to increase the separation between the outer layers where the
bending stresses are highest, thus increasing the panel's resistance to bending. As a result, thicker
panels can span greater distances under the same loads. In bending, the maximum stress occurs
in the outermost layers, one in tension, the other in compression. Bending stress decreases from
the maximum at the face layers to nearly zero at the central layer. Shear stress, by contrast, is
higher in the center of the panel, and zero at the outer fibers.
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3. "Wiring" redirects here. For the software development platform, see Wiring (development
This article is about building wiring. For power distribution, see electric power transmission and
electric power distribution.
Three-phase copper cable TN-S 16 mm2 with PVC insulation
Electronic symbols for wiring
Building wiring is the electrical wiring and associated devices such as switches, meters and light
fittings used in buildings or other structures. Electrical wiring uses insulated conductors.
Wiring safety codes vary by country, and the International Electrotechnical Commission (IEC) is
attempting to standardize wiring amongst member countries. Wires and cables are rated by the
circuit voltage, temperature, and environmental conditions (moisture, sunlight, oil, chemicals) in
which they can be used. Colour codes are used to distinguish line , neutral and ground (earth)
Armoured cables with two rubber-insulated conductors in a flexible metal sheath were used as
early as 1906, and were considered at the time a better method than open knob-and-tube wiring,
although much more expensive.
The first polymer-insulated cables for building wiring were introduced in 1922. These were two
or more solid copper electrical wires with rubber insulation, plus woven cotton cloth over each
conductor for protection of the insulation, with an overall woven jacket, usually impregnated
with tar as a protection from moisture. Waxed paper was used as a filler and separator.
4. Over time, rubber-insulated cables become brittle because of exposure to atmospheric oxygen, so
they must be handled with care, and are usually replaced during renovations. When switches,
outlets or light fixtures are replaced, the mere act of tightening connections may cause hardened
insulation to flake off the conductors. Rubber insulation further inside the cable often is in better
condition than the insulation exposed at connections, due to reduced exposure to oxygen.
Rubber insulation was hard to strip from bare copper, so copper was tinned, causing slightly
more electrical resistance. Rubber insulation is no longer used for permanent wiring installations,
but may still be used for replaceable temporary cables where flexibility is important, such as
electrical extension cords.
About 1950, PVC insulation and jackets were introduced, especially for residential wiring.
About the same time, single conductors with a thinner PVC insulation and a thin nylon jacket
(e.g. US Type THN, THHN, etc.) became common.
Diagram of a simple electrical cable with three insulated conductors
The simplest form of cable has two insulated conductors twisted together to form a unit; such
unjacketed cables with two or three conductors are used for low-voltage signal and control
applications such as doorbell wiring. In North American practice, an overhead cable from a
transformer on a power pole to a residential electrical service consists of three twisted (triplexed)
wires, often with one being a bare wire made of copper (protective earth/ground) and the other
two being insulated for the line voltage (hot/line wire and neutral wire). For additional safety, the
ground wire may be formed into a stranded co-axial layer completely surrounding the phase
conductors, so that the outmost conductor is grounded.
5. Batten Holder
Product Code: 210303
Depth: 67 mm
Bulb Fitting: Bayonet Cap (BC)
Room: Living Room
Mount Type: Wall
ASTA approved batten holder for use with BC lamps.
ASTA approved batten holder for use with BC lamps.
Straight batten holder
Rated at 2 amps
Use with BC fitted lamps
White colour matched with Wickes Trade pack wiring accessories
The ASTA mark indicates that products have been independently tested to the latest
standards and is a sign of quality and reliability to both trade and home users.
6. In electrical engineering, a switch is an electrical component that can break an electrical circuit,
interrupting the current or diverting it from one conductor to another.
The most familiar form of switch is a manually operated electromechanical device with one or
more sets of electrical contacts, which are connected to external circuits. Each set of contacts can
be in one of two states: either "closed" meaning the contacts are touching and electricity can flow
between them, or "open", meaning the contacts are separated and the switch is nonconducting.
The mechanism actuating the transition between these two states (open or closed) can be either a
"toggle" (flip switch for continuous "on" or "off") or "momentary" (push-for "on" or push-for
A switch may be directly manipulated by a human as a control signal to a system, such as a
computer keyboard button, or to control power flow in a circuit, such as a light switch.
Automatically operated switches can be used to control the motions of machines, for example, to
indicate that a garage door has reached its full open position or that a machine tool is in a
position to accept another workpiece. Switches may be operated by process variables such as
pressure, temperature, flow, current, voltage, and force, acting as sensors in a process and used to
automatically control a system. For example, a thermostat is a temperature-operated switch used
to control a heating process. A switch that is operated by another electrical circuit is called a
relay. Large switches may be remotely operated by a motor drive mechanism. Some switches are
used to isolate electric power from a system, providing a visible point of isolation that can be
padlocked if necessary to prevent accidental operation of a machine during maintenance, or to
prevent electric shock.
7. What is Intermediate switch, its construction, working principle and using in different
wiring (lighting etc) circuits?
There are four terminals in intermediate switch by which it changes the flowing of
current from one circuit to another circuit (fig1). It’s ON and OFF the supply by two
ways. The four terminals of intermediate switch is shown in fig 1 label as A, B, C, D. In
some cases, the terminal contacts of switch is meet terminal A with terminal C and
terminal B meet with terminal D as shown in fig 1 a.
9. Stair case wiring circuit diagram, OR How to control a lamp from two
different places by two ,2-way switches?
Stair case wiring circuit diagram, OR How to control a lamp from two different places by
two ,2-way switches?
Staircase wiring circuit diagram very simple
This is the staircase wiring circuit diagram. Here we can control a bulb from two
different places by using two, 2-way switches.
Now consider this circuit diagram. In this case you can see that circuit is
complete and bulb is ON. Suppose you want to OFF bulb from the upper switch at top
of stair, simply Switch OFF the switch then circuit will break and the bulb will be OFF.
You can switch ON the bulb again to switch ON this Switch. In other words you can
OFF and ON bulb from upper switch at the top of stair. Obviously; you can do same
from the upper and bottom switch, so let’s see how we can do that from that switch at
the bottom of stair.
Now return to circuit again in the pic, In this case you can see that circuit is
complete and bulb is ON. Suppose you want to OFF the bulb from the lower switch at
bottom of stair. Simply OFF the switch, then again circuit will break and the bulb will be
OFF. You can switch ON the bulb again to switch ON this Switch
This is a stair case circuit diagram by which we can control a bulb from two
different places.We can switch OFF and Switch ON the bulb from both switches at the
same time. in other words we can control (OFF or ON) the bulb from upper and lower
10. This will be more useful and will have a very simple explanation