Question { 3597 }

explain LED lamps?

Answer

A Light Emitting Diode lamp is a solid state lamp (SSL)
that uses light-emitting diodes (LEDs) as the source of
light. Since the light output of individual light-emitting
diodes is small compared to incandescent and compact
fluorescent lamps, multiple diodes are used together. LED
lamps can be made interchangeable with other types, but the
presently at a higher cost. Most LED lamps must also
include internal circuits to operate from standard AC
voltages. LED lamps offer long life and high efficiency,
but initial costs are higher than for flurorescent lamps.

Question { 4352 }

What is Grounding?

Answer

In electrical engineering, ground or earth may be the
reference point in an electrical circuit from which other
voltages are measured, or a common return path for electric
current, or a direct physical connection to the Earth.
Electrical circuits may be connected to ground (earth) for
several reasons. In mains powered equipment, exposed metal
parts are connected to ground to prevent contact with a
dangerous voltage if electrical insulation fails. A
connection to ground limits the voltage built up between
power circuits and the earth, protecting circuit insulation
from damage due to excessive voltage. Connections to ground
limits the build-up of static electricity when handling
flammable products or when repairing electronic devices. In
some telegraph and power transmission circuits, the earth
itself can be used as one conductor of the circuit, saving
the cost of installing a separate return conductor.

For measurement purposes, the Earth serves as a
(reasonably) constant potential reference against which
other potentials can be measured. An electrical ground
system should have an appropriate current-carrying
capability in order to serve as an adequate zero-voltage
reference level. In electronic circuit theory, a "ground"
is usually idealized as an infinite source or sink for
charge, which can absorb an unlimited amount of current
without changing its potential. Where a ground connection
has a significant resistance, the approximation of zero
potential is no longer valid. Stray voltages or earth
potential rise effects will occur, which may create noise
in signals or if large enough will produce an electric
shock hazard.

The use of the term ground (or earth) is so common in
electrical and electronics applications that circuits in
vehicles such as ships, aircraft, and spacecraft may be
spoken of as having a "ground" connection without any
actual connection to the Earth.