h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: Electricity - A1013248
Author: Bob McBob - U222236

Hello? Anyone There?

Hmm, the main problem I can see with this is it's a virtually endless subject... with the Title 'Electricity' people are going to be asking questions like
- "Why haven't you included a section on the various gases used to insulate High Voltage Switchgear"

Personally I'd be a little less ambitious and aim for a smaller target... trying to explain everything there is to explain about electricity could (and generally does) take whole text books


Whisky

They'd probably be group VIII, right?

There, consider the section included!

On reading at a glance, it looks very good - particularly well-linked. Well done!

Unfortunately, I lack the technical know-how to be able to comment much further than that...

Hmmmmmm.... Now I am one of those guys who would say this Entry need more depth. On the other hand it's a nice introduction.

I spotted a minor thing:

Electricity is not an enregy - like pressure is not an energy. It can be used to generate energy, though.

I think I'll bring some more comments later on...

FF

Oh, just one thing to check with your links though... The rules for edited entries say you can't link from an edited entry to an unedited one...

How about a title change though... something along the lines of "A basic introduction to Electricity"... that would leave the opportunity for more in-depth entries to be added later on.


Oh, and one other point... DC Transformers do exist... they're called choppers.

Here's one:

You could add that the term 'electricity' was coined by English pysicist William Gilbert (1544 - 1603) based on the Greek word 'elektron' for amber. Gilbert re-discovered what the Greeks had already observed, namely that amber could attract small stuff like dust particles when rubbed with a piece of fur.

FF

You mention volts and amperes, but what about ohms?

and some typos:

Alternating Current *wich* switches direction very fast

If you use positively charged particles, *if* goes in the same direction

What about metric units for those of us in the rest of the world?

Hi,

I think there's a problem with this (but I always had a problem with units)...

"Power is the energy used per second, measured in Watts. It is equel to the voltage times the current (P = I x V)."

Power is power - period. Power is what comes out of the drive wheels of my car. Energy is what I pay for and put in the tank. It's a 200 HP (149.2 KW) car even when it's standing still.

Similarly a Watt is a Watt. Time does not factor into it.

A power station outputs, at any given instant, Megawatts. If you "draw" 1000 Watts for an hour to POWER your electric fire, then you pay for a Kilowatt Hour of ENERGY.

Awu

I don't see any wrong,

power = energy / time
watts = joules / seconds
kilowatts = killowatt hours / hours

The only bit I don't like is "Semiconductors, which is something with a resistance that goes down as it gets hotter. You don't need to think about this unless you have a PhD in Life, the Universe and Everything."
As semiconductors are so fundamental to computing and electronics, they deserve a better description.

The rest should be fine with a few spelling corrections.

MP

What I was trying to say was...
"Power may be measured at any point in time, whereas energy has to be measured during a certain period, e.g. a second, an hour, or a year. " (From "How Stuff Works" -I think.)

If you and I both weigh 100Kg and we run up stairs and I get there first. I had more POWER. But we both expended the same amount of energy because we raised 100Kg through 10M.

So I agree that Power is the rate of energy transfer. I suppose I'm having a problem with the statement...

Power IS energy USED per second.

Maybe
Power is energy produced per unit time, or the rate of energy transfer.



I agree about the semiconductors. The increase of Rho with temperature isn't the defining attribute of a semiconductor. It has to do with quantum physics, energy levels, etc. etc.


Awu.

The units are just fine. Energy is a more basic unit than power in the SI system.
What you have in your tank has the potential of being converted to energy, which will enable your car to realise its potential for delivering power.

Uh... re-iterating so it doesn't get lost in the b/log:

Electricity is not an energy. (This is stated in the beginning of the Entry)

HELL

>Electricity is generally the flowing of electrons through a conductor, such as a Wire

-- I don't think so. It's like a wave effect, it's not as though electrons actually move along the conductor.



>There is also Static Electriciy, not covered on this page.

-- Lightning is the result of static elec, but it is mentioned below!



>Sources of Electricity
>Power Stations
>Batteries
>Lightning
>Magnets, by use of Electromagnetic Inducation

-- a) Lightning is not the source. The clouds are the source, the lightning is the discharge of it.

-- b) Magnets are not a source of elec in the same way that power stations are. It's like saying that coal is the source of elec.



>Current is subdivided into two categories:

-- AC and DC are not 'categories' of current. They simply say something about the way the current flows. And AC doesn't necessarily change direction quickly.



>Voltage is the energy held by one coulomb of electrons

-- No. Voltage is an electromotive force or potential difference.

>Voltages are measured in Volts.

-- EMF or PD can be measured in Volts.



>They step up or down voltage by converting electriciy to magnetism, then back to electriciy again.

No. Talk about induction instead.



>Power is the energy used per second, measured in Watts.

-- No. Power is not 'per second' - that is consumption. And it may be measured in watts or in voltamps.

So kW or kVA is not the same as kWh or kVAh.

Just my

Bels

Hi Bels (and HELL)

(HELL'S BELLS!!!)

Bels said...

"-- No. Power is not 'per second' - that is consumption. And it may be measured in watts or in voltamps."


I think we are trying to say the same thing. Finally someone who agrees with me

I was also tempted to say something about the categories of current too, but couldn't put my finger on exactly what was wrong. I agree with what you said though.

Awu.

I still don't see why you have a problem with this Ausnahmsweise

power is energy per unit time, it can be per second, per week, per iceage, or whatever.

power used is energy used per unit time
power produced is energy produced per unit time

So if my computer draws 100 watts, it uses 100 joules per second. Use it for an hour and I have consumed 0.1 kilowatt hours of energy.

We seem to be saying the same thing. Are you not being a little picky insisting on a certain definition, saying 'per unit time' instead of 'per second'?

Are voltamps an american thing? That's not an expression I've seen very often, anyway it's exactly the same thing as watts (by definition).

>So if my computer draws 100 watts, it uses 100 joules per second. Use it for an hour and I have consumed 0.1 kilowatt hours of energy.

-- Precisely. And there is the distinction. The computer 'draws' 0.1 kW. Use it for one hour and it 'consumes' 0.1 kWh. The distinction being made is between kW and kWh. So you could say that kW is the rate at which elec is used, while kWh is the amount used. Something like the distinction between speed and distance?

>Are voltamps an american thing? That's not an expression I've seen very often, anyway it's exactly the same thing as watts (by definition).

No, and no. Not specifically US, generally used in UK and Europe to my certain knowledge. For inductive loads (eg motors, fluorescent lights, arc welders, fridges, aircon, even computers with voltage transformers and fans), not the same thing as watts. But outwith the scope of this entry.

Static electricity isn't, it's simply a charge. When this is discharged you have an electric current, like in lightning, or the shock you.
The dictionary seems to disagree with me though and lable static charges as electricity as well. Bugger.


Maybe Ausnahmweise et al. are confusing themselves with the concept of kWh which seems to be power*time, but really isn't. The more basic unit is energy and 1 kWh devolves to 3.6MJ.

Bob,

I'm surprised there isn't already an entry on electricity, but this is a good one. There are few places you'll have to tidy up before it's ready.

1. Although electricity may not technically be a form of energy, I'd leave it stand as you have it, because it is a form of energy to most people.

2. You mention in a footnote that batteries are collections of cells, but elsewhere you talk about 1.5 being the voltage of a battery, which it isn't. It's the voltage of a cell. I think you should do away with the distinction between batteries and cells and call them all batteries, as everybody does nowadays. You can add a footnote saying that technically the 1.5V ones are cells if you want.

3. Semiconductors - the thing that makes them semiconductors is not that they change resistance with temperature, it is that they conduct slightly. Most things either conduct electricity freely or not at all.

4. 'Current is said to flow in the opposite direction to the charge'. Firstly, this is confusing. It's the sort of detail that doesn't really add to the knowledge of the reader. You could say 'current is said to flow from positive to negative, even though usually it in fact consists of negatively charged particles flowing in the opposite direction'. Secondly, in America they have the opposite convention: current is said to flow from negative to positive, so it flows in the same way as the electrons, but the opposite direction to positive ions in a battery.

5. Your section on voltage is very confused. Voltage is not the energy held by one coulomb of electrons. That may be the definition of a volt (I can't remember) but it is not a definition of voltage. You'd be better to explain it by analogy, as 'electrical pressure, the thing that pushes electricity around and makes it flow'.

6. Transformers look like big plugs - only the smallest ones do. Transformers come in a range of sizes from tiny ones that look like big plugs up as far as ones the size of houses that sit outside Power Stations humming quietly to themselves.

7. The ratio of the number of turns - more information that is not informative. You haven't given enough context for this to mean anything, so cut it out or explain in more detail.

8. The names of units of measurement do not have capital letters. We say W as the abbreviation, but the name is watt without a capital W. Similarly, A is for ampere, with no capital A and no accent on the e.

9. 'Current is the rate flow of electrons'. You should leave out the word 'rate' in this.


Some typos:

inducation --> induction
conduators --> conductors
wich --> which
equel --> equal

Sorry to belabour this, but I think it's important and we still seem to have a disconnect. (And I'm not confusing KW and KWH )

Everything we measure (Henries, Farads, Ohms, Volts, Watts) boils down to some combination of Meter/Kilogram/Second (MKS).

It's true, power is Nm/s.
Energy is Nm.

But this doesn't mean you can "equate" the two.

Suppose Fred has a million dollars. Joe earns $1000/week. I can't deduce anything about Fred's salary, even though at first glance salary is money per week.

KVA and KW. Bels was on the right track. For inductive and capacitive loads the current leads or lags the voltage (C.I.V.I.L is how we remember it. Capacitive - I leads V. Inductive (L) - V leads I). The Cosine of the angle between the two is the power factor. It's not a North American thing.

Think of a railway wagon. You can pull it from straight ahead. All your energy goes into moving it. If you have to stand to the side at an angle, only part of your energy goes into forward motion. Your electricity meter measures and you pay for KVAH. You get usefull work out of the KWH. For a purely resistive load the two are the same. Something heavily inductive may have a large ballast capacitor to attempt to bring the power factor closer to 1.

Awu.