Question

Two lamps, one rated 100 W at 220 V and the other -
in parallel to electric main supply of 220V. Find the
. The figure below shows three cylindrical copper condi
Compare the resistance and the resistivity of them
of 220V. Find the current drawn in each lab​

Answer 1

Answer:

Resistance R of each lamp from given power P and operating voltage V is obtained from the relation,

P = ( V2 / R ) ....................... (1)

Hence resistance of 100W, 220 V lamp = (220×220)/100 = 484 Ω

Resistance of 200W, 220 V lamp = (220×220)/200 = 242 Ω

when lamps are connected in series , equivalenet resistance = 484+242 = 726 Ω

Hence current drawn by lamps that are connected in series = 220/726 = 0.3 A

When lamps are connected in parallel, each lamp draws current independenly as per its wattage.

Current drawn by 100 W lamp = 100/220 = 0.45 A

Current drawn by 200 W lamp = 200/220 = 0.91 A

Hence total current drawn by lamps when they are connected in parallel = 0.45+0.91 = 1.36 A