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A Simple Guide to Energy and Thermodynamics

By: Dr Gareth Evans - Updated: 16 Oct 2012 | comments*Discuss
 
Energy Electricity Heat Light Wind

These days everyone seems to be talking about energy, whether it’s the rising cost of electricity, gas and petrol, carbon costs and offsets, alternatives to our traditional sources or what happens when the oil finally runs out. Going a little bit deeper, however, and trying to get to grips with what’s really going on when we generate electricity or burn fuels, calls for an understanding of a little bit of science – and specifically the field known as thermodynamics.

If, like many, you have rather hazy memories of your school science lessons, or worse still, bad memories of the whole experience, and the very mention of the word has already started to put you off reading any further – relax! The name may sound intimidating, but the basic ideas are very simple to grasp. No, honestly, they really are.

OK – so here come the three laws of thermodynamics.

The First Law

Despite its impressive-sounding title, the First Law really doesn’t tell you anything you don’t already know – you can’t get something for nothing! That said, it is a vitally important part of understanding energy and what happens when one form is converted into another.

The key thing to remember is that energy generation isn’t the same thing as creating ‘new’ energy; all you’re doing is changing one kind of energy for another – the kinetic energy of moving water being turned into electrical energy in a hydro-electric power station, for example.

This law is also the basis for one of the most important ideas in physics – the Conservation of Energy Principle. This states that the total amount of energy in a closed system remains constant over time, bringing us back to the original idea that you don’t create energy or destroy it, you just swap it for a different kind.

The Second Law

The Second Law of Thermodynamics isn’t any harder to understand; just think of it as the universe’s version of foreign exchange. In just the same way as you never get the full value of your Pounds in Euros or Dollars and you always lose a bit on the deal, converting energy from one form to another is never 100 percent efficient. Some of the energy ends up ‘lost’ in the transformation – usually as heat.

If you take the example of a wind turbine, although most of the kinetic energy of the moving wind is converted into electricity, friction in the moving parts means that some of it is converted into heat energy and effectively lost from the system. This law also explains the problem with conventional incandescent light bulbs; in this case, around 98 percent of the electrical energy is converted into heat, with only two percent going to do the job it was really designed for in the first place!

The Third Law

This one gets even easier. It’s the equivalent of a universal rule that says ‘no cheating!’ Put simply, there’s no way around the other two – no matter how hard you try – which makes the basis for all those claims of perpetual motion machines look more than a tad shaky!

So that’s it – the three laws of thermodynamics in a nutshell. See; told you they weren’t all that scary.

Universal Principle

These laws are fundamental to understanding much of the ‘why’ that surrounds energy and the way we use it. There’s a lot more to them than has been covered here, of course, but even with the benefit of this simple guide, most of the big issues of energy efficiency should become much easier to grasp. It’s not every day that you get to grips with one of the guiding principles of the universe, but that’s effectively what these laws are, and they apply everywhere, even when you get into the heady realms of Einstein’s Relativity or Quantum theory.

As for those, well, they really are a little more complicated to explain!

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you need more on the second law =)
ncis - 31-Jan-12 @ 8:15 PM
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