EMC Question of the Week: April 2, 2018
You’re relatively safe in a car during a thunderstorm because,
- lightning won’t strike cars with rubber tires
- the car battery neutralizes any charge build-up on the car
- the radio antenna acts like a lightning rod
- the metal body and frame creates a Faraday Cage around you
Answer
The correct answer is "d." If you are in a metal car with a metal roof and lightning strikes the car, currents will be routed on the body of the car around you in a manner that prevents strong fields from forming inside the car. This effect is often referred to as the Faraday Cage effect.
The other choices make no sense. It doesn't matter what a car's tires are made of; lightning currents won't flow through the tires anyway. After breaking down up to a mile of air to reach the car, lightning will break down the air beneath the car to reach the ground. Also, a car battery can't neutralize charge and a radio antenna makes a poor lightning rod (especially given that it has no connection to earth ground).
By the way, if your car is a convertible, it doesn't make a good Faraday cage. Seek shelter from the storm elsewhere.
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