Saturday 30 August 2014

Phone chargers and the environment

A plugged-in phone charger with no phone attached does use electricity - but not very much.

We are often warned of the dangers to the environment of leaving phone chargers plugged into the mains because they are still using current. This can seem a little counter-intuitive. After all, an electrical socket doesn't leak electricity when there's no plug in it, so why should a phone charger, if there is no phone attached?

Unlike the socket, the charger has something at work even if there is no phone present. The charger has to convert the high voltage AC current of your mains down to the low voltage DC used to charge a phone. This involves passing the mains current through a transformer, and transformers have two complete electrical circuits, one for the input and one for the output. This means that the input circuit does use power, even if there is no device to receive the output. (Contrast this with the electrical socket, where the circuit is broken unless something is plugged in.)

However, the power usage of such a charger when not in use is tiny - around 0.1 watts. Compare that with a traditional bright light bulb at 100 watts - it's 1/1000th the amount. So by all means unplug your phone charger when not in use, but don't think it's going to make a big difference. You can do far, far more by switching to LED light bulbs, fitting double glazing, turning the heating down by 1 degree, insulating your house better and all the other ways that are traditionally recommended for saving energy.

Monday 25 August 2014

What happens to fingernails and hair after death

I have included this slightly gruesome story under 'fun' rather than 'health' as it isn't a matter of practical concern, just curiosity.

It's often said that human fingernails and hair continue to grow after death, allowing artists who specialise in the grotesque to envisage strangely hairy and long-nailed corpses. In a sense 'grow' is the wrong word for these extremeties made up of a tough, structural protein called keratin (skin, hooves, horns and beaks are also made of different assemblies of keratin). This is because they aren't alive, so can't strictly grow, but rather are constructed by specialist cells in the body.

If we get past the word, though, the idea itself has no basis. The processes that produce hair and nails require a living body to provide the raw materials and to power the production with glucose. Although there aren't any detailed scientific studies testing for this, there is no reason to think that hair and nails would continue to grow, as there is no mechanism to 'power' their production once the body has died. It's a myth.

It has been suggested that the myth originated because skin contracts as it dries and may seem to make hair and nails a little longer a little while after death. According to the British Medical Journal, the myth has certainly been around since the late 1920s, when it was mentioned in the novel All Quiet on the Western Front.

Saturday 2 August 2014

Does water go off?

There is often amusement caused by seeing bottled water with a 'best before' or 'use by' date. Surely water doesn't go off? 

It's a neat paradox that pure water doesn't go off - but water still should only be consumed relatively soon after obtaining it.

This goes both for tap water, once poured, and bottled water, once opened. In both cases it is best kept in the fridge and should be consumed within a couple of days. It's not that water itself can degrade. It's a very simple chemical compound, H2O - surely about the best known there is - with one oxygen atom and two hydrogen atoms. And the water itself will be exactly the same after a year. The trouble is that lots of living things need water, and like water as an environment in which to live. There are plenty of airborne bacteria, fungus spores and more that are floating around all the time. Once water is exposed to air it will start to accumulate these and, over time, you will get yourself a nice colony, some of which is likely to be bad for you.

If you have no choice but to drink water that has been kept for more than a couple of days (of course, unopened bottled water is fine up to its best before date), boil it for several minutes first.