Module 3

1. Module 3

1.23. Lesson 4

Module 3 Lesson 4

Module 3—Electrical Phenomena

Lesson 4—Electric Fields

Get Focused

The photo shows an aircraft in flight, with a lightning strike in the background.

Have you ever been on an airplane as it flew through a lightning storm? You may have seen an eerie blue glow on the wing tips. This unusual effect is an electrostatic phenomenon called St. Elmo’s fire.

St. Elmo’s fire was thought to indicate good luck to sailors in ancient times, because the tall masts of the ships would sometimes glow with a blue light following a bad storm. They believed it was a sign of salvation from the patron saint of sailors, St Ermo—the mispronunciation of the saint’s name was given to the fiery glow.

Although it is generally harmless, St.Elmo’s fire may have played a role in an airplane crash in 1959; an airplane flew into a stormy Italian sky and crashed just 12 minutes later.

The investigators who examined the crash site concluded that the accident was likely caused by an electrical discharge from St. Elmo’s fire, which they suspected had ignited vapors from the aviation fuel. The accident prompted Lockheed, the aircraft’s manufacturer, to install a flame-arrester screen on the vent pipe openings of its aircraft to eliminate the potential for St. Elmo’s fire to become a bad omen in stormy skies.

Though such accidents can now be prevented, St. Elmo’s fire still shows up on airplane wing tips and propellers. The explanations of this phenomenon involve the effects of strong electric fields.

In this lesson you will answer the following essential questions:

What is an electric field, and how can it be described and analyzed?
What exactly is St. Elmo’s fire, and why does it occur at the end of pointed surfaces?

Module 3: Lesson 4 Assignments

Your teacher-marked Module 3: Lesson 4 Assignment requires you to submit a response to the following:

Assignment—A 1, A 2, A 3, and A 4
Discuss—D 4

You must decide what to do with the questions that are not marked by the teacher.

Remember that these questions provide you with the practice and feedback that you need to successfully complete this course. You should respond to all the questions and place those answers in your course folder.