Electrical Engineering

Methods of Arc Extinction in Circuit Breaker High resistance method Low resistance or current zero method.

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Factors Affecting Corona in Power System As mentioned earlier, the line voltage of the conductor is the main determining factor for corona in transmission lines, at low values of voltage (lesser than critical disruptive voltage) the stress on the air is too less to dissociate them, and hence no electrical discharge occurs. Since with increasing voltage corona effect in a transmission line occurs due to the ionization of atmospheric air surrounding the cables, it is mainly affected by the conditions of the cable as well as the physical state of the atmosphere.

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Two positive charges repel each other, as do two negative charges. On the other hand, opposite charges attract each other.

Benjamin Franklin carried out extensive electricity research in the 18th century, inventing the lightning rod amongst his many discoveries. In the event of a lightning strike, the lighting rod conducts the strike through a grounded wire, protecting the building.

Electric fields work in a similar way to gravity. Whereas gravity always attracts, electric fields can either attract or repulse.

Did you know that electricity plays a role in the way your heart beats? Electricity causes muscle cells in the heart to contract. Electrocardiogram (ECG) machines, used by medical professionals, measure the electricity going through the heart. As the heart

Coal is the world’s biggest source of energy for producing electricity. Coal is burned in furnaces that boil water. The steam from the boiling water then spins turbines that are attached to generators.

Have you ever wondered why birds sitting on a power line don’t get electrocuted? If a bird sits on just one power line it is safe. However, if the bird touches another line with a wing or a foot, it creates a circuit, causing the electricity to flow through

Lightning is a discharge of electricity in the atmosphere. Lightning bolts can travel at around 130,000 miles per hour and reach nearly 54,000 °F in temperature.

Electricity travels at the speed of light -- more than 186,000 miles per second!

The amount of damage done by the electric shock depends not only on the magnitude of the current.

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The armature of D.C. generator is laminated to? anonymous poll (d) reduce eddy current loss – 31 👍👍👍👍👍👍👍 74% (a) reduce the bulk – 6 👍 14% (b) provide the bulk – 3 👍 7% (c) insulate the core – 2 ▫️ 5% 👥 42 people voted so far.

Which of the following could be lamina-proximately the thickness of laminations of aD.C. machine ? anonymous poll (c) 0.5 m – 12 👍👍👍👍👍👍👍 63% (b) 0.05 mm – 7 👍👍👍👍 37% (a) 0.005 mm ▫️ 0% (d) 5 m ▫️ 0% 👥 19 people voted so far.

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Electrical Conductivity of Materials It is the property of material which represents that how easily the electricity can be conducted by the material. It is denoted by ‘σ’. It is the reciprocal of resistivity of material. It unit is mho/meter.

State change temperature are of following types- Melting point- It is the temperature (in oC or K) at which the substance changes from solid state to liquid state. Boiling point- It is the temperature (in oC or K) at which the substance changes from liquid state to gaseous state. Freezing point- It is the temperature (in oC or K) at which a liquid changes from liquid to solid state. Theoretically it is equal to the melting point. However, practically there may observed some difference.

Ferromagnetic Materials These materials are having very large and positive susceptibility to external magnetic field. They are having a strong attraction to external magnetic field and are able to retain magnetism even after remove of external magnetic field. This property of materials is called magnetic hysteresis. Example: Iron, Cobalt, Nickel. Paramagnetic Material These materials are having very small and positive susceptibility to external magnetic field. In the presence of external magnetic field, these materials attains very small magnetism. Example: Aluminum, Platinum, oxygen, Air etc. Diamagnetic materials These materials are having very weak and negative magnetic susceptibility to external magnetic field. On application of external magnetic field these are repelled slightly by external magnetic field. These materials does not retains the magnetism after removal of external magnetic field. Mostly all metals i.e. silver, copper, gold, hydrogen etc. are diamagnetic materials. Antiferromagnetic materials These materials are having very small and positive susceptibility to external magnetic field. In the presence of external magnetic field these materials get slightly magnetized in the direction of external magnetic field. In these materials, atoms are having mixed parallel and anti parallel aligned magnetic dipole movement.  Example: Cr, MNO, FeO, CoO, NiO, Mn etc. Ferrites These materials are having very large and positive magnetic susceptibility like ferromagnetic materials. These materials are generally compound which are having more complex crystal structures than a pure material. As compare to ferromagnetic materials, ferrites are having lower magnetic saturation.  Example: Fe3O4, BaO.6Fe2O3 etc.