MadSci Network: Physics

Re: Are you safe in a car during a lightning storm?

Area: Physics
Posted By: Paul Odgren, Instructor, Cell Biology, University of Massachusetts Medical School (Dept. of Cell Biology)
Date: Tue Aug 26 12:59:02 1997
Area of science: Physics
ID: 870969289.Ph
Dear Kay and Christen,

The answer is, "it depends." 

Lightning is really a huge spark, and it can kill you. It's made up of a 
stream of electrons, which are one kind of the three particles that make up 
atoms. Electrons each have one bit of electric charge. There are two kinds 
of charge, called positive and negative, and electrons all have negative 
charge. Positive and negative (opposite) charges attract each other VERY 
strongly, and like charges (positive and positive, or negative and 
negative) repel each other just as strongly. Because electrons push away 
from each other, they tend to run around the OUTSIDE of a metal object like 
a car when they are passing through, like during a lightning strike, to 
get as far away from each other as possible. That is, even if you touch the 
INSIDE of a car that's being hit by lightning, all that electricity will be 
on the OUTSIDE surface, and you won't even feel it. BUT!!!!!! NEVER TRY 
THAT!! Because, not all car bodies are made of metal any more, a lot have 
plastic or fiberglass parts, and some metal things inside the car might be 
connected just right to the outside and allow you get a shock. But in 
general, inside a metal car, if you keep out of contact with door handles, 
switches, and so on, yes, you are quite safe inside a car during a 
lightning storm.

The Museum of Science in Boston, Massachusetts gives a wonderful 
demonstration of this every day. They have a giant static electricity 
generator three stories high that makes HUGE sparks - not quite as big as 
real lightning, but 20 feet or more long! Some of them jump to what looks 
like a giant bird cage. From inside the metal cage, a person explains about 
lightning, electricity, and sparks. While these sparks are hitting the 
cage, the demonstrator runs his or her hands along the inside of the cage 
to show that the electricity is all running around the outside, which 
explains why that person remains perfectly safe. It also explains why you 
are safe inside a metal car. But a car during a lightning storm is not a 
carefully controlled laboratory environment, so keep your windows closed 
and your hands away from handles if you're on the road when a storm hits! 
And find out if your car has a metal body.

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