What Is...?

What is Alternating Current?

Electricity comes in two flavours: Direct Current and Alternating Current. With Direct Current (DC) electrons flow along a wire like water along a pipe. With Alternating Current (AC) electrons vibrate back and forth (less than ten-thousandth of a millimetre) but they don't go anywhere. Imagine a long pipe, at one end there's a plunger being moved rapidly in and out. A plunger at the other end would move in and out in sympathy. The water isn't travelling along the pipe but energy is. That's how it is with alternating current. With both DC and AC, when the wire narrows it gets harder for the electrons to travel or wiggle and everything gets hot and the wire glows - eureka, the light bulb.

What is Global Warming?

Global Warming means just that: the earth is getting warmer. Average temperatures have been creeping up for decades. Most scientists think this is because there is now more carbon dioxide (CO2) in the atmosphere. CO2 is given off when anything burns - coal, petrol, gas. CO2 (and other "greenhouse gasses" like methane) cause more of the sun's energy to be retained by the earth, so the earth gets warmer. People are worried because higher temperatures cause ice to melt and sea levels to rise, and cause changes in weather patterns. Reducing the amount of CO2 emitted means using less energy per person, switching to non-CO2-emitting forms of energy generation such as wind, solar or nuclear, or reducing world population.

What is Bird Flu?

Bird Flu is an influenza virus that birds catch. Usually they recover. However, a strain of the bird flu virus know as H5N1 is much more lethal to birds. People are worried about bird flu H5N1 because humans can catch it from direct contact with infected birds or with their droppings and over half the people who have caught it have died. Luckily H5N1 does not spread from person to person. But if a strain of H5N1 developed that was able to pass from person to person it could rapidly spread around the world. Until such a virus emerges (if ever) it's impossible to say how deadly it would be to humans or how easy it would be to catch it. Clearly, a deadly and easy-to-catch virus could cause millions of deaths.

What Is...? Questions

If you have a "What Is...?" question please email it to mike at hraconsulting-ltd.co.uk.