Upload
melina-blake
View
220
Download
5
Embed Size (px)
Citation preview
www.bzupages.com
PRESENTATION ON: ELECTROMAGNETISM
TOPIC: INSULATORS
PRESENTED TO: DR. TARIQ BHATTI
BSIT 3RD SEMISTER BZU
www.bzupages.com
GROUP MEMBERS
NIMRA IRSHAD
06-27
SADIA RASHEED
07-13
www.bzupages.com
INSULATORS
• An insulator, also called a dielectric, is a material that resists the flow of electric current.
• Substances that have very high resistance, of the order of many megaohms are classified as insulators.
www.bzupages.com
• A material with atoms in which the electrons tend to stay in their own orbit is an insulator because it cannot conduct electricity very easily
• In insulators, all the electrons are bound with their respective atoms and cannot move freely
• Because electric current does not flow through them
www.bzupages.com
• Some solids e.g, wood diamond etc have very low conductivities ranging between 10-10 and 10-20 are called insulators
www.bzupages.com
EXAMPLES OF INSULATORS
• WOOD
• PLASTIC
• GLASS
www.bzupages.com
• AIR• VACUUM• RUBBER• MICA• OIL• DRY PAPER• TEXTILE FIBERS
www.bzupages.com
• Moist earth is a fairly good conductor, while dry, sandy earth is an insulator
• Pure water is a good insulator but salt water is not
www.bzupages.com
Types of insulators
• GLASS INSULATORS:• Glass insulators were
first produced in the 1850's for use with telegraph lines.
• As technology developed insulators were needed for telephone lines, electric power lines, and other applications.
www.bzupages.com
• In the mid 1960's a few people began collecting these antique insulators.
• Today there are over 2000 collectors. • Insulator clubs, local and national shows, and good
reference books are available
www.bzupages.com
NIMRA IRSHAD
06-27
www.bzupages.com
PLASTIC INSULATORS
• Plastic insulators are made from a high-grade polypropylene or polyethylene material.
• They come in many sizes and shapes, to fit all types of permanent and temporary posts.
• • Plastic insulators are not
as long-lasting as porcelain
www.bzupages.com
• but they have quickly taken over the market due to their reasonable cost
• . Their only real 'enemy' is ultraviolet light, which causes them to become increasingly brittle with age
www.bzupages.com
• SOME OTHER FIGURES ARE SHOWN BELOW
www.bzupages.com
RUBBER INSULATORS
• Rubber insulators consist of a wire-retaining flat strip that is mounted on a flat insulating rubber pad.
• The assembly is long enough to wrap half-way around a corner or end post.
• These rubber insulators are made to withstand the extreme pull of high-tensile wire
www.bzupages.com
• SOME OTHER RUBBER INSULATORS ARE SHOWN BELOW
www.bzupages.com
PORECELAIN
• Fireproof and impervious to sunlight, porcelain insulators have been around the longest
• Porcelain is expensive, which is why they are being used less and less.
www.bzupages.com
• Porcelain insulators tend to develop tiny cracks ('crazing'), which fill up with soil and moisture.
• Crazing reduces the insulating quality.
www.bzupages.com
ADVANTAGES OF INSULATORS• Fiberglass is
inexpensive as fiberglass is made from silica sand, an abundant resource
• . Fiberglass insulation does not burn or shrink.
• Fiberglass insulation also has good acoustic properties for sound absorption.
www.bzupages.com
• Fiberglass insulation has some environmental benefits as well
• The US Environmental Protection Agency requires all new fiberglass insulation to incorporate 20 percent recycled glass.
www.bzupages.com
DISADVANTAGES OF INSULATORS
Does not stop radiant heat transfer
Potential health risks such as lung damage
Need an additional vapor barrier to protect it from moisture
Resistance to heat transfer drops dramatically when wet