Question

Two electric bulbs P and Q have their ratio in the ratio 1:2.They are connected in series across a battery.find the ratio of the power dissipation in these bulbs?

i need this answer

Answer 1

2:1

Explanation:

The power dissipated in a circuit component of resistance `R` is described by either of the two expressions:
`P = V^2/R` or `P=I^2R`
The two seem to be contradictory at first glance - since the first one apparently says that the power is inversely proportional to `R`, while the second one says that it is, on the contrary, directly proportional.

Of course, there is no real contradiction here - in each case, the power depends on another quantity besides the resistance - and so the power is inversely proportional to `R` - but only when the `V` remains the same, and it is, on the other hand, directly proportional to `R`, but only when `I` remains the same.

When bulbs are rated, their power ratings typically assume that they are going to be connected across the same voltage (the mains voltage). Thus, if the power ratings for the two bulbs are in a ratio 1:2, then their resistances are in a ratio of 2:1.

If the two bulbs are connected in series, then the same current flows through both of them. Thus, their power outputs will be in the ratio 2:1.