Question { 6683 }

Q. calculate the value of the resistor to be connected in series with a 100W;
230V lamp so that the wattage of the lamp is reduced to 35W

Answer

lamp 100W/230v
when resistor R is connected in series with the lamp.
lamp power=35W
lamp Voltage= 230V /* since 230v is the operating voltage of the lamp*/
series current = 35/230
=0.152 A
power dissipated at a resistor = 100 W -35 W
= 65 W
= Isqr X R
R= 65/(0.152sqr)
= 2.8 kilo-ohm