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

Who is Online

We have 122 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

Peru

 

 

In October 2011 our little group: Sonia, Craig, Wendy and Richard visited Peru. We flew into Lima from Rio de Janeiro in Brazil. After a night in Lima we flew to Iquitos.

Read more ...

Fiction, Recollections & News

His life in a can

A Short Story

 

 

"She’s put out a beer for me!   That’s so thoughtful!"  He feels shamed, just when he was thinking she takes him for granted.

He’s been slaving away out here all morning in the sweltering heat, cutting-back this enormous bloody bougainvillea that she keeps nagging him about.  It’s green waste tomorrow and he’s taken the day off, from the monotony of his daily commute to a job that he has long since mastered, to get this done.  

He’s bleeding where the thorns have torn at his shirtless torso.  His sweat makes pink runnels in the grey dust that is thick on his office pale skin.  The scratches sting as the salty rivulets reach them and he’s not sure that he hasn’t had too much sun.  He knows he’ll be sore in the office tomorrow.

Read more ...

Opinions and Philosophy

The Meaning of Life

 

 

This essay is most of all about understanding; what we can know and what we think we do know. It is an outline originally written for my children and I have tried to avoid jargon or to assume the reader's in-depth familiarity with any of the subjects I touch on. I began it in 1997 when my youngest was still a small child and parts are still written in language I used with her then. I hope this makes it clear and easy to understand for my children and anyone else.

Read more ...

Terms of Use                                           Copyright