4 electrical & electronics students

Nano pine trees University of Wisconsin materials scientists    grew these lead-sulfide nano wire in the shape of pine trees. With a main trunk and branches spiraling around it like a helical staircase. Structures like this were difficult to make –until the researchers found that a single screw shaped dislocation embedded in the trunk wire causes a spiral of branches to sprout.

What is the effect of temperature on resistance? ·          Resistance of pure metals increases with the increase in temperature. ·          Resistance of some alloys increases slightly with the increase in temperature. ·          The resistance of electrolytes , insulators such as paper, rubber , mica, etc decrease with rise in temperature.

HOW DO YOU CONSIDER   3-PHASE SUPPLY BETTER THAN SINGLE PHASE SUPPLY? ·           In 3-Φ power is smooth , which is not so with 1- Φ ·          3- Φ motors are self-starting while 1- Φ motor s are not. ·          Pf of 3- Φ supply is la rge as compared to 1- Φ supply.

How will you determine that the given instrument can be used on AC or DC or both . If the scale is cramped at the beginning of scale , the meter can be used on AC or DC or both . if the whole scale is  uniformly distributed  the meter is a moving coil instrument and can be used on D.C only.

How will you determine that the given instrument can be used on AC or DC or both . If the scale is cramped at the beginning of scale , the meter can be used on AC or DC or both . if the whole scale is   uniformly distributed   the meter is a moving coil instrument and can be used on D.C only.

Why is the transmission or distribution voltages always multiple of 11 e.g 33000,6600,11000,440..etc. The above   values are at the sending end and include an allowance of 10 % for line drop , giving voltage at the receiving end of 33,000 6,000 10,000 ,400volts etc

What do you under stand from transmission and   distribution of electricity Transmission means wire carrying high voltages for very long distances. transmission voltage in india is   1,32,000v 33,00 volts. Distribution means the feeding   of various load points at desired places at medium or low voltage.voltage is 11,000. 6600 v   ,440 volts.

   function of  booster                               i t regulates the feeder voltage independently  and  raises it if desired.

 why  is the 3-phase 4 wire  system used nowadays? since it can supply hv to motors and other power loads while low voltage to domestic consumers.

Megger     T he "Megger" instrument for measuring the insulation resistance of electrical devices was introduced by the British firm of Evershed and Vignoles in 1905. The name comes from the fact that the insulating resistance of a properly-designed appliance is in the range of tens and hundreds of meghoms. The crank on the end powers a DC generator connected to a specially-designed meter. The instrument, sold in the United States by Biddle of Philadelphia, was presented to the Greenslade Collection by Daniel Chaucer.      The Megger is used with "Evershed's Patent Direct Reading Resistance Box" when measuring resistances in the sub-megohm range.

What is hunting in synchronous machine? Answers.com  >  Wiki Answers  >  Categories  >  Sports  >  Hunting and Shooting  >  What is hunting in synchronous machine? Answer:   in the process of hunting when a DC generator(alternator) is subjected to a sudden change in load(in the stator) causes the rotor to hunt for a new equilibrium position(let us take the example of a pendulum when its made to oscillate with a general push it oscillate with a particular amplitude and frequency and after its oscillation, reaches the mean position, but as a certain load say 2gms is applied to the pendulum, oscillation changes and pendulum tries to attain a new amplitude and frequency as the applied load suggests)similarly in the case of alternator as the load changes rotor attains a new equilibrium position say of a particular degree(z)and the degree of rotation changes from(0 to 360 pre...