Two electric bulbs A and B rated 200V~100W and 200V~60W are connected in series to a 200V line.Then the potential drop across
1)Each bulb is 200V
2)100W bulb is greater than that across 60W bulb
3)100W bulb is smaller than that across 60W bulb
4)Each bulb is 100V

Dear Student,

Please find below the solution to the asked query:

Given information is,

first bulb rating is 200 V - 100 W. So, the resistance of the first bulb is,

P1=V12R1  R1=V12P1=2002100=40000100 R1=400 Ω

second bulb ratings is 200 V - 60 W. Therefore,

P2=V22R2  R2=V22P2=200260=4000060 R2=20003 Ω

Therefore, when two bulbs are connected in series, the effective resistance is,

Reff=R1+R2  Reff=400+20003=1200+20003 Reff=32003 Ω

So, current in the circuit is,

i=VReff=20032003=6003200 i=316 A

The potential drop across each bulb is,

across 100 W bulb is,

V1=iR1=316×400=3×25 V1=75 V

across 60 W bulb is,

V2=iR2=316×20003 V2=125 V

So, the potential drop across 100 W bulb is less than that of the potential drop across 60 W.


Hope this information will clear your doubts about the topic.

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