Help with basic electricity problem.

[BigOlWilly]

The question:
Four 60W, 240V light bulbs are connected in parallel. If these lights were to be placed in series, what voltage and power rating would each have to be in order to produce the same amount of power?

 

I know I'm meant to explain what I've tried but the confusing thing is that if 60W light bulbs are placed in series, each one would have 60v thus 1A will flow through so the power would be the same as the parallel circuit?

 

Thanks for the help!

[studiot]

The question:

Four 60W, 240V light bulbs are connected in parallel. If these lights were to be placed in series, what voltage and power rating would each have to be in order to produce the same amount of power?

 

I know I'm meant to explain what I've tried but the confusing thing is that if 60W light bulbs are placed in series, each one would have 60v thus 1A will flow through so the power would be the same as the parallel circuit?

 

Thanks for the help!

 

Let's consider the power question first, since it doesn't make sense as it stands.

 

"to produce the same amount of power?"

 

"If these lights were to be placed in series"

 

You can't place the same lights in series to produce the same amount of power.

 

Either you place different lights of a different power rating in series to produce the same amount of power as 4 x 60W bulbs in parallel

 

or

 

You place the same lights in series and obtain a different power.

 

[BigOlWilly]

 

Let's consider the power question first, since it doesn't make sense as it stands.

 

"to produce the same amount of power?"

 

"If these lights were to be placed in series"

 

You can't place the same lights in series to produce the same amount of power.

 

Either you place different lights of a different power rating in series to produce the same amount of power as 4 x 60W bulbs in parallel

 

or

 

You place the same lights in series and obtain a different power.

 

I think I'm suppposed to find the first option. I think I'm misinterpreting the question in my textbook.

I worked out that changing the voltage to 960V while keeping the same power rating will work. Right? But I think it's the wrong answer cause the question is asking for a different power rating.

Edited January 24, 2017 by BigOlWilly

[studiot]

A good idea would have been to post the exact words from your textbook.

 

However if the power is to be the same, by definition, the power rating must be the same ie 4 x 60W (assuming all the new bulbs are the same).

 

Note that the power rating of a mains electric device is only correct at its rated (ie mains) voltage.

In the UK both voltage and current are printed on the bulb.

 

Since the bulbs are now in series, what do you think the voltage across each one now is?

[BigOlWilly]

A good idea would have been to post the exact words from your textbook.

 

However if the power is to be the same, by definition, the power rating must be the same ie 4 x 60W (assuming all the new bulbs are the same).

 

Note that the power rating of a mains electric device is only correct at its rated (ie mains) voltage.

In the UK both voltage and current are printed on the bulb.

 

Since the bulbs are now in series, what do you think the voltage across each one now is?

Each bulb will have 60V across it if connected to 240V.

Here is the question word for word:

Bill and Mary are discussing the lighting for their living room. At present they have four 60W, 240V light bulbs in parallel. Bill suggests that it might be cheaper to replace these four bulbs wired in series.

If this was to be done, what would be the voltage and power rating of each of the new bulbs they would need in order to produce the same amount of power.

Thanks for the quick replies BTW.

[studiot]

So if in the series configuration each bulb has 60 volts across it and produces 60 watts and, as you say, has 1 amp current through it,

 

What is its resistance?

 

What will then be the wattage it produces if connected to 240 volts? (assuming it does not blow)