Static Electricity

Have you ever touched a door knob as you are about to open a door or perhaps touched the door of an automobile as you are about to enter it and received a “shock” that startled you, maybe even hurt a little bit?  If so, then you have come in contact with static electricity.  Movement creates friction that causes free electrons to collect in abundance on some objects.  For example:  Rubbing a glass rod with a silk handkerchief will give up electrons to the silk, creating a negative charge to the silk and a positive charge to the rod.  Sometimes, just walking across a rug in a room can create a charge of static electricity in your body that will startle you when you touch something. 

The microcircuits in the microchips used in electronic devices such as computers are very sensitive to static electricity.  There is a huge industry that has evolved to cope with this problem.  Static electricity is caused by a buildup of electrons in an object.  It occurs when the buildup of free electrons in the object balance with another object.  A static discharge from small objects has very little current and will only startle you if you touch them.  If the object is very large, perhaps an airplane that has just landed from a trip in the sky, the static electricity buildup can be great enough to harm.  Aircraft ground crews attach a special “grounding cable” to the aircraft before touching it after it parks.  They want to be sure that no spark occurs when they connect the refueling hose.

Lightning

The ancient Greeks believed that Thunder and Lightning were tools of their Gods.  Today, some 2500 years later, we know that Lightning is electricity.  Lightning is created when a large potential difference builds up between two or more areas of matter, air in the sky is matter, and the motion of large areas of air create large potential differences; then when these areas of air equalize their potential difference, and it happens very quickly, we see the lightning and hear a thunder clap.  The lightning is the energy transferred to balance the potential difference of the air (matter).  This electrical burst of energy generates heat and instantaneously creates an air gap along the electrical discharge path; when the surrounding air claps back together to fill the gap, you hear the Thunder that accompanies the lightning flash. 

Lightning is a form of static electricity, but much more dangerous due to the very large amount of unbalanced electrons (Direct Current)and very high difference of potential (High Voltage) that build up by the atmospheric friction of wind in the air.  The brief but high current and voltage in a lightning strike can kill. When lightning strikes electronic equipment, it may catch it on fire, and it usually it burns out the microcircuits and interconnecting wiring.

An excerpt from the Encyclopedia Britannica says that the potential difference between the cloud and ground can be in the order of 10 to 100 million volts with peak currents of 30,000 amperes at a temperature of 50,000 degrees Fahrenheit.

Occasionally an article in the newspaper will tell about an unfortunate person that was struck by lightning, and most of the time, the newspaper reports that they were killed by it. The Dallas Morning News of September 25, 2004 has a sad story about a young football player having been killed by a lightning strike on the practice field.  Some of his fellow players were also injured by the strike.  The article says it happened during a late afternoon rain shower.

Another article in the DMN, August 15, 2006 reported that two 9th graders hiking in Colorado were caught in a shower and struck by lightning. One was knocked completely unconcious and burned seriously. and the other boys legs were briefly numbed. He remembered learning CPR from his health class and his actions helped to save his friend. After a stay in the hospital where they were taken, both slowly recovered.

Benjamin Franklin determined that lightning was “electricity” with his kite experiments.  In his day, sailing ships were frequently struck by lightning as well as homes that people lived in.  He invented the lightning rod as a method to protect lives and property from the destructive effects of lightning. 

In the 20th Century, Nicola Tesla, the inventor of our AC power system, experimented with lightning in his laboratory in the mountains of Colorado.  He created apparatus that would attract lightning. 

I have read that lightning precedes a thunder storm by 30 minutes or more.  Evidence of approaching thunderstorm activity should give you warning to seek shelter.  (Never seek shelter under a tree). When lightning strikes a tree, the heat generated within the tree by the burst of energy can split the tree in half.  When lightning strikes a utility power transformer, it can shut off the electricity to a neighborhood.

There is a simple way that you can judge the distance between yourself and a flash of lightning.   You see the flash of lightning first because light travels much faster through air than sound.  Count the seconds that elapse between the flash of light and the resulting sound, multiply by 1100, this will give an approximate distance in feet.

Lightning is useful, but aiso a dangerous and destructive force of nature that commands respect and fear. Mother Nature uses lightning to clean the atmosphere and promote rain. She also uses it to start forest fires to burn off sections of dry brush. This causes problems for some National Parks and when people place housing additions in areas where seasonal brush grows abundently in dry climates.

Nobody knows how much the Ancients knew about lightning and static electricity. Their Records are very scarce and most were not preserved. Since lightning can be life threatening, I suspect that lightning was as much of a consern to the Ancients as it is to us now.