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PRESENTATION ON: ELECTROMAGNETISM

TOPIC: INSULATORS

PRESENTED TO: DR. TARIQ BHATTI

BSIT 3RD SEMISTER BZU

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GROUP MEMBERS

NIMRA IRSHAD

06-27

SADIA RASHEED

07-13

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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.

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• 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

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• Some solids e.g, wood diamond etc have very low conductivities ranging between 10-10 and 10-20 are called insulators

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EXAMPLES OF INSULATORS

• WOOD

• PLASTIC

• GLASS

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• AIR• VACUUM• RUBBER• MICA• OIL• DRY PAPER• TEXTILE FIBERS

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• 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

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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.

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• 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

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NIMRA IRSHAD

06-27

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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

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• 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

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• SOME OTHER FIGURES ARE SHOWN BELOW

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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

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• SOME OTHER RUBBER INSULATORS ARE SHOWN BELOW

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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.

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• Porcelain insulators tend to develop tiny cracks ('crazing'), which fill up with soil and moisture.

• Crazing reduces the insulating quality.

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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.

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• Fiberglass insulation has some environmental benefits as well

• The US Environmental Protection Agency requires all new fiberglass insulation to incorporate 20 percent recycled glass.

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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