A question for you sparkies & fizzicists

[AndyR]

I'll put this here rather than in "Tech" cos it's got nowt to do with geetars :lol:

I wonder if any of you chaps could settle a thing in my mind?

Scenario: Occasional light fitting (one that plugs into a wallsocket), that has a dimmer control - some sort of variable resistor, I assume.

Question: Does the appliance actually use less energy if you turn the dimmer down? ("Less energy" as in "saving-the-planet" and "saving-my-pennies")

Human intuition says "yes" to me, but... is intuition correct in this case?

I can remember V = IR, so I know that the thing will draw less current if you turn it down, but I can't remember any other equations...

Will reducing the current also reduce:

a) The amount of money clocking up on the bill?

b) The amount of energy that must be generated at the other end to run the appliance?

And, are these two actually the same thing?



... I've probably opened a can of worms here :lol: (:twisted:)

[MrBump]

I'm no sparkie, but I assumed that the resistor would send current to earth?  That would mean the same current draw, just dissipating it to another location...

[Plexi Ken]

http://answers.yahoo.com/question/index?qid=20070808215433AADEaIs

[MDV]

Resistors dont divert current to earth, they inhibit its flow with materials that have higher resistivity.

Its power thats the concern anyway, and thats I^2R or V^2/R, in watts, which means that the power draw with twice the resistance but the same emf is half. In general power is work done (energy converted from one form to another) divided by the time taken, so obviously using a dimmer will reduce the rate of work of your lights (or whatever else)

An explanation:

With a resistor in place the total current of the path is reduced (if in series), so if you start with

+------Light bulb------ -


With V and R

I=V/R
P=I^2/R=(V/R)^2/R=V^2/R

and go to

+----resistor----light----- -

with an addtional R that we'll say is equal to the first for simplicity/illustrative purposes then you get
I=V/2R...blah blah blah....P=V^2/2R, P1=2P2

Yeah. The pot should reduce actual power consumption of the appliance. The EMF inhibited still has to go somewhere though, and that is heat in the resistor, so maybe not, all told.

Rates are measured in KWh, so kilowatt values over an hour, so a 1KW appliance running for an hour is 1KWh, so tarrif and standing periodc charges allowing what you spend is proportional to how much power you draw.

How much youre saving the planet is debatable. Putting dimmers on lights while America still exists and does what it does is kind of like turning up to car crash with a dust pan and brush ;)

[Twinfan]

Dimmers are no good with the low energy bulbs we now have to use, so I'd just swap bulbs.  Much easier!

[MDV]

Dimmers are no good with the low energy bulbs we now have to use, so I'd just swap bulbs.  Much easier!

That is a much better idea. Do they still have that horrible dull yellow light though? Stupid low energy electron recombinations.

[Twinfan]

They are a bit yellow I guess.  Doesn't bother us though.

[Will]

Dimmers are no good with the low energy bulbs we now have to use, so I'd just swap bulbs.  Much easier!

I believe heavy duty \ industrial 100w bulbs are still legal?
NRG saving one sgive me migraines :(

[Philly Q]

Can't offer anything scientific, but I have noticed when you turn dimmers down they usually hum or buzz.  Which gives the impression that something is working harder.  And it's bloody annoying.

[MDV]

Can't offer anything scientific, but I have noticed when you turn dimmers down they usually hum or buzz.  Which gives the impression that something is working harder.  And it's bloody annoying.

I believe thats ones that switch on and off.

[MDV]

They are a bit yellow I guess.  Doesn't bother us though.

I had them for a couple of years in my previous place because the wiring was done by a chimp with a soldering iron and bulbs blew once every few days (basically whenever the guy downstairs switched anything on). I got used to it, but I was really pleased to get back to decent white light of real bulbs.

One thing I'll give them - they last forever. Never had one break on me.

[Dreichlift]

You can get daylight balanced energy saving bulbs that give off a more natural blue light, however they're not that common and more expensive.

[AndyR]

Nice to see there are some kindred spirits here :D

The reason I ask is because, as a temporary measure, we have such a fitting in the (windowless) kitchen off of our office (the strip light blew while I was on holiday apparently, and instead of replacing it, tech support have brought us one of the lamp stands from the training room as a stop-gap :roll:).

Now, someone keeps turning the bloody thing down, I'm guessing, for "energy saving reasons". I can live with it, but I don't like it that much - I loathe "low" or "yellow" electric light when I'm trying to do something. I'd rather have (even extremely low) natural light, or good old "f@ck off 100W" bulbs, anything else I feel like I'm straining my eyes and can't see properly (sometimes gives me headaches as well, Will).

Before I start any battles, though, I thought I'd see if could find out if we actually were saving any energy by having "seduction lighting" in our office kitchen (in comparison to the as yet unfixed strip light... I know the answer's no, but that's another matter :lol:)

Elsewhere, I am getting used to these cr@ppy low energy things - but I do not like or approve of them in any shape or form :lol:

I'm not actually that interested in "saving the planet", by the way, I don't think we can without a good bit of culling. I'm more of a "there are finite resources, once we've used them up, they'll be gone... duh??" kind of guy. Reducing the amount of energy we use as individuals isn't going to change what's coming, it'll just slow the arrival down a bit...

My wife will tell you I'm actually quite, er, "anti-green" - but in my defence, we don't own or drive a single car, or buy newspapers/magazines, we don't have a dishwasher, we prefer jumpers to turning the heating up, and I personally haven't flown or been abroad (or intend to fly or go abroad) in something like 15 years... All the things one is meant to cut down on to reduce one's personal carbon footprint - I don't bluddy do anyway!!!


... nah, my question was for pure and higher motvies - gathering ammo for a potential office feud :lol:


EDIT: This came while I was waffling:

You can get daylight balanced energy saving bulbs that give off a more natural blue light, however they're not that common and more expensive.

That's interesting, I'm a part-time artist as well (not done much for a few years, though), and seeing as my spare time is often at night, one NEEDS "daylight" bulbs otherwise you can't get colour right... I discovered the other week that the missus had used up my last daylight bulb a while back for her desklight (she didn't know what a "daylight bulb" was) - I was wondering whether such a thing existed or was even possible under these new regulations...

[AndyR]

http://answers.yahoo.com/question/index?qid=20070808215433AADEaIs

CLASS!!!

Just followed this link.... thanks... :D

For those, like me, slow to follow links:
"Early dimmers worked using a variable resistor. They actually used more energy when the lights were dimmed than when they were on bright. They also heated the wall up.

Modern dimmers work by switching the electricity off and on thousands of times per second. They use much less energy than the older dimmers. With these modern dimmers you will use less energy than if the lights were on bright.

They call this switching pulse wave modulation. They dim the lights by making shorter pulses with longer gaps between them."

(Of course, I realise these are "internet facts", but that's good enough for me :lol:)

Now, a new question - the dimmer for this beastie is a little "foot-pedal" thingy with a slider on it. It is warm, but it is emitting a jolly little buzzing noise...

The second point (buzzing) makes me think it's a modern dimmer?? Is that a reasonable assumption folks? (Obviously, I want it to be not-modern, so it's not actually too good for my purposes...)

Oh well...

[ToneMonkey]

Did you know that it's now illegal to make or import 100W lightbulbs in/into the UK.  Came through the other day.