Question

Two lamps of 200W,220V and 100W,220V are connected in series across 220V supply.The ratio of current through them will be

Answer 1

Answer:

1.36 Amp

Explanation:

Resistance of 1st lamp, R1 = V1²/P1 = (220)²/100

= 484 ohm

Resistance of 2nd lamp, R2 = V2²/P2 = (220)²/200

= 242 ohm.

If lamps are connected in series ,

Req = R1 + R2 = 484 + 242 = 726 ohm

So, I = V/Req = 220/726 = 20/66 Amp = 10/33

= 0.3 amp

If lamps are connected in parallel combination,

Req = R1R2/(R1 + R2)

= 484 × 242/(484 + 242)

= 484 × 242/726

= 44 × 242/66

= 4 × 242/6

= 484/3 ohm

So, I = V/Req = 220/(484/3) = 660/484

= 60/44 = 15/11 = 1.36 Amp