Electrical Engineering

A spur is an extension connected from some point along the main circuit of an electrical installation. Spurs are sometimes called 'tees'.

The initial condition of a capacitor that has no energy stored is zero volts.

The initial condition of an inductor that has no energy stored is zero amperes.

torque/weight ratio of an instrument indicates sensitivity.if a pointer is having less weight, it will be having high torque/weight ratio so that even for a very small deflection pointer starts moving and indicates measured value.

assuming that the electrons travel very close to C (the speed of light, i.e. 299 792 458 m / s) then simply using:Wavelength = Velocity / frequency

it is given:

Wavelength @50Hz= (299 792 458 (m*sec-1))/(50 (sec-1))=599584917 m = ~6000km

(remember that once the distance gets to factors of 25%, 50%, 100%, 125% ... of the wavelength, funny stuff happens to your transmission line due to the equivalent impedance at the receiving point!)

Index or Glossary

Since capacitive reactance is inversely-proportional to the supply frequency, as the frequency is increased, the reactance will decrease.

yes i think so

Yes, there are flashing l.e.ds. An ordinary l.e.d. can, of course, be flashed on and off by interrupting the current through it. There are products such as the LED-FLASHDIM available from LED-SUPPLIES.COM that will enable you to control how LED strip lighting flashes and at what speed and brightness levels

it can not be use for heavy duty motors as well as it requires a high starting current.

In the UK, the letters, 'R-Y-B', stand for 'red-yellow-blue' which are the colours used to identify the lines (not phases) of a three-phase transmission or distribution cable. The colours are also used, in some cases, to identify the corresponding bushings for transformers, circuit breakers, voltage transformers (potential transformers), etc., in substations. The sequence of these letters/colours also correspond to the normal phase sequence of the three-phase system.

In UK residential, commercial, and industrial installations, these colours have now been replaced by the EU harmonisation colours: brown-black-grey.

Other countries use different methods of identifying line conductors, including 1-2-3, A-B-C, R-S-T, L1-L2-L3, etc., or various combinations of these methods.

Surge diverters are normally located on the terminal pole of an overhead line system, and are intended to protect terminal equipment (e.g. transformers, cables, etc.) from sudden surges in voltage. Each of the line conductors is normally connected to earth, via the surge diverter.

Under normal circumstances, the internal resistance of the surge diverter is high enough to insulate the line conductor from earth. However, if a voltage surge occurs due, for example, to a lightning strike, then the resistance of the surge diverter will collapse, 'diverting' the surge to earth.

Take the internal series resistance of the voltage source and make it the internal parallel resistance of the current source. Then compute using Ohm's law the current of the current source to be equal to the maximum current the original voltage source could supply a short circuit load.

Note: the two sources are equivalent.

what is the value of the smallest division on a ammeter

No. The capacitor may improve its power factor by altering the effective reactive power of the machine, thus reducing the current drawn from the supply.

yes

'Line conductors' are the three 'hot' conductors (A-B-C) that connect a three-phase supply to a three-phase load. In some cases, a pair of line conductors (e.g. A-B, B-C, or C-A) is used to supply a single-phase load. A 'line fault' can be a short-circuit fault between all three, or any two, of these line conductors -whether they supply a three-phase load or a single-phase load.

To obtain the amp of the copper bus bar, multiply the width of the bus bar by the thickness of the bus bar to obtain the current carrying capacity of the bus bar.

A two-phase* system is archaic, and has been completely superceded by three-phase systems, so there is no demand for two-phase induction motors. (*A two-phase generator has two phase windings, displaced from each other by 90 degrees.)

no,hermetical transformers do not have conservator.

DC motors generally use commutators. Also some single phase AC motors use commutators. They are the type which which have their field windings connected in series with their armatures and they can typically be found in home vacuum cleaners, DIY-type ac electric drills, etc.

if the transformer is distributing transformer then we shoud have to give more prefer to the high volatage to reduce losses

if we distibute power at low volage there is more current which causes more losses

and in hv system there is high volage and low is current so the losses are also low

Whether a transformer is 'step up' or 'step down' has nothing to do with the way its windings are connected, so it could be wye-delta or delta-wye.

You don't calculate the rated kV.A of a circuit breaker; it's determined by the manufacturer. It's important that a circuit breaker's rated kV.A exceeds the fault level kV.A at the point where the circuit breaker is located, otherwise it may fail to interrupt a fault current and, possibly, self destruct.

No. A voltmeter measures potential difference (voltage). To measure power, a wattmeter is required. On the other hand, for a d.c. circuit only, you could use a voltmeter and an ammeter, and multiply their readings in order to calculate the power of a load.