Question

two lamps one is rated 100w at 200V and the other 60W at 220V are connected in parallel to a 220V supply. find the current drawn from the supply line

Answer 1

If this is an text qn then ur qn is wrong..

1.P= 100w and v= 220
2.p=60w at 220v
Using p=vi
P/v =I
100/ 220+ 60/220=160/200

Which is 16/22 =0.727...
Therefore current =0.73 A

Answer 2

Case I

Given:

Power = P = 100 W
Voltage = V = 220v
Resistance = R

    P = V²/R
100 = 220 ×220/R
   R  = 220 × 220/100        
       = 484 Ω

Case II

Given:

  Power = P = 60 W
Voltage = V = 220v
 Resistance = R

  P = V²/R
60 = 220 × 220/R
 R = 220× 220/60   
     = 806.7 Ω

As the resistors are connected in parallel , 
total resistance = 1/R
1/R = 1/484 + 1/806.7     
      =  806.7 + 484/484×806.7     
      = 1290.7/390442.8
  R = 390442.8/ 1290.7
      = 302.5 ohms     

Total resistance = 302.5 Ω

Then,

     I = current
    V = IR
220 = I × 302.5
     I = 220/302.5 
       = 0.73 A

The current drawn is 0.73 A


:) Hope this Helps !!!