if 100W and 200W bulbs are connected in series to a supply
which bulb will glow brighter and why

Answers were Sorted based on User's Feedback

Answer / neeraj

100W bulb will glow brighter.
Suppose they are first connected individually (to find their
resistance), we will find that resistance R=V^2/P will be
higher for 100W bulb.
Now, when two bulbs are connected in series, current through
each of them is same so the thermal energy produced per
second i.e. I^2.R will be higher for 100W bulb which
accounts for its high brightness.

Is This Answer Correct ?    44 Yes 4 No

Answer / chaturbhuj poddar

If the rating of two bulbs be as (100W-220V) &(200W-220V)and be connected in series to the same d.c.voltage supply. then the value of current is same in both the bulbs. It can be seen that the resistance of 100W bulb is greater than the resistance of the 200W bulb. Hence, heat produced in 100W bulb is more than produced in 200W.Conclusion: 100W will glow brighter than 200W bulb.

Is This Answer Correct ?    30 Yes 8 No

Answer / guest

100w because resistance will be higher

Is This Answer Correct ?    4 Yes 5 No

Answer / chaturbhuj poddar

Let us suppose that the first bulbs is marked as 100W-200V and the second bulb as 200W-200V, and both are connected in series to 200V d.c. supply to make easy calculation.
Resistance of 100W bulb R1 = V^2/P = 200*200/100 = 400 ohm,
Resistance of 200W bulb R2 = V^2/200 = 200*200/200 =200 ohm
Thus, Resistance of the combination = =600 ohm. current through each bulb = V/600= 200/600 =1/3 A
Heat produced by 100W bulb per second H1=I^2*R1=(1/9)*200J/sec
Heat produced by 200W bulb per second H2=(1/9)*400 J/s.
H2 is greater than H1. Thus, 200W bulb will glow brighter.

Is This Answer Correct ?    12 Yes 38 No

Answer / l.shanmugam

* both are bulbs same bright
* if the bulb are series conection power supply same as
series conection so both are bulbs same bright

Is This Answer Correct ?    7 Yes 35 No

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