With the approach of summer, the great outdoors transformsinto a playground for the physically active among us.
But for those failing to exercise caution, there is one summertime phenomenon that can spoil the fun in a flash - lightning, of course.
Lightning begins with storm clouds, which acquire an electrical charge in ways still unclear to scientists.
The important thing is that the top of the cloud is positively charged while the bottom is negatively charged, creating a strong electrical field that repels electrons at the earth's surface deeper into the ground.
As the electrons are pushed further and further away, the Earth's surface acquires a strong positive charge.
Because of the strong electric field in the cloud, the air around it "breaks down," or separates into positive ions and electrons.
The breakdown increases the distance between the electrons and ions, giving the electrons more freedom to move. This in turn causes air to conduct electricity more easily.
With the added conductivity in the air, all that is needed is a path for the electricity to follow. These paths, called "step leaders," emanate from the cloud in 150-foot sections on their way to the earth's surface.
There, the step leaders meet up with "positive streamers" that emanate from positively charged ground objects into the sky.
Once the connection is made, electrical current is free to travel between the cloud and earth, helping to neutralize the charge separation between them.
This strong charge separation, or static electricity, explains why victims of lightning strikes feel the hairs on the back of their neck stand up.
But this process goes unseen by the human eye. What we recognize as lightning actually is a product of the tremendous heat generated by the electrical current.
This heat, which exceeds the temperature on the surface of the sun, produces the brilliant flash we associate with lightning.
The heat also forces the air around the strike to expand so rapidly that it explodes in the form of thunder.
This is why you can estimate your distance from a lightning strike by measuring the length of time between the lightning flash and the moment you hear the thunder.
Divide the number of seconds by five, and this approximately equals the distance in miles between you and the lightening.
How do traffic lights work?
Anyone who has driven a car can attest to the frustration of sitting at a long traffic light.
While traffic in the other lanes moves freely, you are stuck wondering if it even knows you're there, not to mention whether there are any cops around if it doesn't.
Fortunately, most traffic lights can detect the approach of an automobile, and will change colors accordingly.
Traffic lights typically operate using an inductive loop, which is a coil of wire buried beneath the road's surface. When electric current flows through the coil, the coil begins to develop a magnetic field.
Once the field is in place, current is able to flow freely through the wire. If the source of current is removed, one would expect current flowing out of the wire to cease.
But this is not the case - instead, electric current continues to flow through the wire until the magnetic field dies out. An inductance meter is able to keep track of these changes in the magnetic field.
In the presence of certain metals such as iron, the inductance of the coil will be much greater.
When a car parks over the coil, the inductance meter detects the increased magnetic inductance in the coil and sends an electric signal to a central processing unit, which then decides whether it is safe to give you the green light.
- Compiled by Mike Layfield
(Submit health and science questions to cavdaily@cavalierdaily.com)
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