*take nothing for granted!
Unless otherwise indicated all photos © Richard McKie 2005 - 2015

Who is Online

We have 82 guests and no members online

Translate to another language

 

 

 

The electrically literate may find this somewhat simplified article redundant; or possibly amusing. They should check out Wikipedia for any gaps in their knowledge.

But I hope this will help those for whom Wikipedia is a bit too complicated and/or detailed.

image010
All cartoons from The New Yorker - 1925 to 2004

 

 

Think of water in a hosepipe

 

Electricity is a means of transporting energy from a source, like the wind, to a device you use to exploit that energy, like your electric toothbrush.

The usual way of explaining electricity is to use the simile of the flow of water in a pipe (a current of water).  We are all familiar with a hose pipe.  Its pressure is analogous to the voltage; and the flow of water is analogous to the current. 

 

image032
The author - almost two - learning about currents and voltage

 

The work that can be done in an hour, for example if you use the jet to spin a bicycle wheel or push leaves along a path, is the pressure (like Volts) times the current (like Amps) for an hour. 

You won’t be able to squirt the water from your hose far if there is no pressure or if there is no water.  You need both.  If the pressure falls the water ceases to flow.

It’s the same with a stream (current) of electricity making its way down a conductor; for example a wire. The electrical force acting on an electrical current provides the power to do work.

Most quantities in modern physics are named after an early natural philosopher or inventor.  If we had let tradition do it, each would probably be related by some strange number, like the number of feet in a mile; or pounds in a ton.  But most new physical values use the decimal system (the rationalised MKS or SI units: meter, kilogram, second).

A Watt is a measure of Power; the instantaneous capacity to do work; named after James Watt. 

Under this system we define one Watt as equal to one Volt (electrical  force) multiplied by one Ampere (current); or Amp for short.  Read More...

Using this simple relationship you can easily calculate that 1000 Watts of power (one kilowatt) can be carried by a current of 4.17 amps at 240 volts (240 x 4.17 = 1000)

But the same power requires only 0.002 amps at 500,000 volts (0.002 x 500,000 = 1000).  So when you turn on an electric kettle or toaster it will draw around 4 amps in your home at 240V but only 0.002 amps in the very high voltage grid to bring it from the generator in the power station.

Power exerted for a period of time is called Energy.  Physicists measure energy in Joules (1 J= 1Watt acting for 1 second).  But to get to a smaller working number electricity companies like to measure energy in kilowatt hours (1 kWh =  3,600 kJ = a thousand Watts acting for the seconds in one hour) 

When your bill comes, you get charged for the Energy, the number of kWh* you used, not Power (kW).

 

image012

 

*Terminology:  1000 Wh = 1 killowatt hour (kWh); 1000 kWh=1 megawatt hour (MWh); 1000 MWh = 1 gigawat hour (GWH), 1000 GWH = 1 terawatt hour (TWh).

 

Add comment


Security code
Refresh


    Have you read this???     -  this content changes with each opening of a menu item


Travel

Berlin

 

 

 

I'm a bit daunted writing about Berlin.  

Somehow I'm happy to put down a couple of paragraphs about many other cities and towns I've visited but there are some that seem too complicated for a quick 'off the cuff' summary.  Sydney of course, my present home town, and past home towns like New York and London.  I know just too much about them for a glib first impression.

Although I've never lived there I've visited Berlin on several occasions for periods of up to a couple of weeks.  I also have family there and have been introduced to their circle of friends.

So I decided that I can't really sum Berlin up, any more that I can sum up London or New York, so instead I should pick some aspects of uniqueness to highlight. 

Read more ...

Fiction, Recollections & News

A Discourse on History

 

 

On Australia Day 2011 again we hear the calls: Change the Flag; become a Republic; reparations for the White Invasion...

There are strong arguments for progress in each of these areas but as the following article discusses we first need to ensure that the changes that must be made are indeed progress; that we don't sacrifice that which has been achieved already.

Read more ...

Opinions and Philosophy

Sum; estis; sunt

(I am; you are; they are)

 

 

What in the World am I doing here?

'Once in a while, I'm standing here, doing something.  And I think, "What in the world am I doing here?" It's a big surprise'
-   Donald Rumsfeld US Secretary of Defence - May 16, 2001, interview with the New York Times

As far as we know humans are the only species on Earth that asks this question. And we have apparently been asking it for a good part of the last 100,000 years.

Read more ...

Terms of Use                                           Copyright