Question

2 lamps 1 rated 100w at 220 volt and other 200w at 220 are connected to series in parallel to electric supply of 220 volt.find the current drawn in each case

Answer 1

Given,
lamp 1 ,
Voltage=220v
Power=100w
lamp 2,
Voltage  = 200w
power  = 220v
to find the current:
Solution:
to find the resistance ,
Resistance  =(voltage × voltage) /power
substituting
Resistance for lamp 1  = (220×220)/100
 = 484 ohm
Resistance for lamp 2 =(220×220)/200
 =242 ohm
in a series ,
Current  = voltage /resistance
here: resistance  = resistance for lamp 1 + resistance for lamp 2
484+482
Resistance  = 726 ohm
hence,
Current  =220/726 =0.3 amplitude
In parallel,
Resistance  =(resistance for lamp 1 × resistance for lamp 2)/resistance for lamp 1 + resistance for lamp
 = 4×242/6
RESISTANCE =484/3 ohm
hence,
current =1.36Amp