Two bulbs of resistances R1 and R2 such that R1 > R2. They are connected in series. Which is brighter?

Question

Two bulbs of resistances R1 and R2 such that R1 > R2. They are connected in series. Which is brighter? What would be the case if they were connected in parallel?


~So far what I put is that in the series, the one with the least resistance would be the most brightest because it has more current flowing through it (I=V/R)

~If in parallel, I am not sure


Can you please explain to me the correct answer without using any equations. I am very confused.

Answer 1

No. In series both resistors have the same current. Power (which the brightness comes from) depends on the current squared times the resistance so for the same current the one with the higher resistance (R1) dissipates more power and is brighter.

It is the opposite for parallel because each bulb would take its share of the power based on how low its resistance was. That means that the lower resistance (R2) would hog the current and be brighter.

Answer 2

If you put the bulbs in series, the current flowing through the bulbs is the same, as all of the current goes through each bulb. The voltage drop across each will be different; each bulb will have a voltage drop that is a fraction of the system voltage.

If you put them in parallel, each will have the same voltage drop (the system voltage), and each will then have a different current.

As to which will be brighter, I would assume that the lower resistance bulb (R2) will be brighter, as it will pull more current and result in a higher power output. But if you put the bulbs in series, the power output will be lower for each bulb than if you put them in parallel. In a constant voltage system, lower resistances mean higher power. Placing resistors in series increases the resistance.

The power dissipation for the bulbs in series would not be the same for both bulbs, however, as you need to account for the different voltage drop across each bulb.

Answer 3

The one with the higher resistance. Power(is this case light) is equal to the current squared times the resistance. So the higher resistance one would produce the most light.