# What Happens to the Power Output of Bulbs in Series When Voltage is Halved?

• nil1996
In summary: I2R1500=I2R2if i divide these equations i get R1=R2.But that is not possible.What is wrong in dividing these equations??next--220/(R1+R2)=II am not able to find any value here.
nil1996

## Homework Statement

Two electric bulbs,each designed to operate with a power of 500 watt is connected in series on a 220 volt line.Now if they are connected to a line of 110v then the power generated by each bulb is??

## The Attempt at a Solution

When i solve it i get more variables that equations.
The equations that i have prepared are--
500=I2R1
500=I2R2
if i divide these equations i get R1=R2.But that is not possible.What is wrong in dividing these equations??
next--
220/(R1+R2)=I

"Designed to operate with 500W" is always for some specific voltage. To me, it is unclear which voltage is meant here, I guess 220V or (if the bulbs are designed to be used in series) 110V. In both cases, you can calculate the resistance of the bulbs. That will stay the same* independent of the voltage applied.
At different voltages, the bulbs will use a different power - that's why the question asks to calculate the power.*not exactly, but you can use this assumption

What mbf said.

It's not clear what voltage the bulbs are designed for. eg at what voltage they will consume 500W. You will get different answers if you assume they are designed for 220 or 110V. I would work the problem twice.

Perhaps start by assuming they are 220V rated and using P = V2/R to calculate R.

1 person
CWatters said:
What mbf said.

It's not clear what voltage the bulbs are designed for. eg at what voltage they will consume 500W.
they are designed to consume 500watt power at 220volts but it is asked to calculate power consumed at 110 volts supply.

CWatters said:
Perhaps start by assuming they are 220V rated and using P = V2/R to calculate R.
is the "V" here supply voltage or voltage across the resistors(which will be different).Also what is the "R" here(total resistance or individual).

CWatters said:
What mbf said.
Who is mbf?

@nil1996: V is the design voltage (220V) and P is the design power (500W). As both are for a single bulb, the resulting resistance value is for a single bulb as well.

mfb said:
Who is mbf?

Sorry I typed to fast.

nil1996 said:
they are designed to consume 500watt power at 220volts

It's still not 100% clear but I guess you mean each bulb consumes 500W when each bulb is connected to 220V.

In which case use the equation I posted to calculate the equivalent resistance..

P = V2/R
so
R = V2/P
= 2202/500
= 96.8 Ohms

Note that's for each bulb not for two in series or anything like that.

but it is asked to calculate power consumed at 110 volts supply.

Now work out the power when connected as per the question.

## 1. How do bulbs connected in series affect each other's brightness?

When bulbs are connected in series, the current through each bulb is the same. Therefore, adding more bulbs in series will decrease the overall brightness of each bulb because the same amount of current is being distributed among more bulbs.

## 2. Can bulbs connected in series have different wattages?

Yes, bulbs connected in series can have different wattages. However, the bulb with the highest wattage will draw more current and may burn out faster than the others.

## 3. What happens if one bulb in a series circuit burns out?

If one bulb in a series circuit burns out, the entire circuit will break and all the bulbs will turn off. This is because the circuit is incomplete without a complete path for the current to flow through.

## 4. How does the voltage affect bulbs connected in series?

The voltage in a series circuit is divided among all the bulbs. This means that each bulb will receive a fraction of the total voltage, depending on the number of bulbs in the circuit. For example, in a series circuit with three bulbs and a 12V battery, each bulb will receive 4V.

## 5. Can bulbs connected in series have different resistances?

Yes, bulbs connected in series can have different resistances. However, the total resistance in a series circuit is equal to the sum of all the individual resistances. This means that if one bulb has a higher resistance, it will require more voltage to pass through it and may appear dimmer than the other bulbs.

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