Question { 4252 }

why the supply frequency in india is 50hz?

Answer

mostly electrical power is generated by running alternators with the help mechanical turbine. and turbines gives best efficiency in the speed range of 3000rpm to 3600rpm.
and frequency of generated electricity is given by
f=((P*N)/120)Hz, P= No. of poles of alternator, N= Speed in rpm.
and mostly 2 poles alternators are used.
therefore ((2*3000/)/120)=50
that's why some countries have selected 50Hz (using 3000rpm) and some 60Hz (3600rpm).
and India has selected 50Hz using 3000rpm.

Question { 13002 }

two bulbs of 100w and 40w respectively connected in paralel
across a 230v supply.which bulb will glow bright and why?

Answer

Obviously 100W bulb will glow brighter because voltage
across both bulbs are same but current flowing through 100W
bulb will be more compared to 40W and power of 100W bulb
will b more.