Question { HP, 10755 }

what is isolation Transformer?

Answer

slaludin i just want 2 make u correct
optocoupler can operate at d.c
and u can not use transformer on d.c

yes purpose of both are same,but both are meant 4 diff.
cnditions

Question { GE, 24053 }

WHY HUMMING SOUND OCCURED IN HT TRANSMMISSION LINES ?

Answer

it is due to d magneisation n dmgntsn of d condutor due 2
wch lngth inc n decr.
study diff bw hmmng n hssng sound 1st

Question { 33552 }

a bulb of 100W and anather bulb of 200W , rated supply
voltage 230v.when supply voltage is reduced to 100v,which
bulb will give more light? and why with calculation?

Answer

p=v^2/r
now in both cases whtevr the voltage ,it is same for both
bulbs.
now the main culprit is r,the bulb which has more
resistance would glow dimmer as per above formula.
we have used the above formula bcaz ,elctrcl instruments
are designd for constant voltage.
as power is inversely proportonal to the resistance (above
formula)therefor 200w bulb would have less resistance and
glow more

Question { 23570 }

what is the frequency standard with tolerance level for India?

Answer

tolerance+/-1%

Question { NTPC, 46089 }

Why Human body feel Electric shock ?? n in an Electric train
during running , We didnt feel any Shock ? why

Answer

in a train we take one terminal 4m the overhead lines and
2nd trough wheel to rails.it means the whole train is
grounded and no chance of shock

Question { NTPC, 46089 }

Why Human body feel Electric shock ?? n in an Electric train
during running , We didnt feel any Shock ? why

Answer

prashant what abt if i travel in engine coach.
the Q is y dont v get shock,,

Question { APTransco, 38953 }

WHERE IS THE LIGHTING ARRESTER SHOULD BE PLACED IN
DISTRIBUTION LINES?

Answer

please 1st visit any substation
in 220 kv substation lightnng arrstr are installd at both
incoming and out going sides
also at both sides of power transformer

Question { 17991 }

if two bulb of 50w &30w apply in series having 230v the
which bulb glow bright ,why

Answer

bulbs or any domestic electrical equipments are designd for
constant voltage,thats why we have parallel connections at
home.and r designd for the formula given below intentionally
we know that p=v^2/r
now p is inversely proportional to r
now we can easily tell 50w bulb will have less resistance
than 30w bulb
now in series, current in both will same,,,,,,so by formula
p=i^2R,,,,,
we can say 30w bulb will glow brighter

Question { 24426 }

what is the difference between a feeder and a cable?

Answer

u can consider every feeder as a cable but u cant say same
as in case of cable.
a feeder is related with load i.e current or we can say
that current capacity i t can bear.
e.g
1.trunk feeder
2.sub feeders
a trunk feeder is a feeder which comes directly 4m the
grid,,,,for e.g lets say 11kv
sub feeders are originated from trunk feeder e.g a11 kv
line is connected to a bus bar and 4m that several 11 kv
feeder are originated.
3*300 size cable we use in feeders now days for 11kv
3 means 3 core and 300 sq mm cross section area of each
core.
while in case of distribution we generally relate it with
voltage regulation,,and it is again with the help of cables.
so we have concluded that all are cables but when we
specify their roles we just call them with seprate names