Concept featured in film: Lightning

DVD: 1:33:55 - 1:40:57

Summary of clip: The scene opened with Doc Brown climbing the clock tower to reconnect the wire that was plugged when the tree snapped and fell on it. The weather is very stormy, with rain, wind, and lightning in the background. Doc is struggling to plug the two wires together. When he does, the wire unplugs at the other end, so Doc must slide down the clock tower to ground level, to reconnect this end of the wire. At that moment, lightning strikes the lightning rod on the clock tower and passes through the wires into the time machine being driven by Marty.

Connection of flickclip to the concept: This is a great clip to initiate a discussion on lightning, lightning rods and lightning safety.

Suggestions to Teachers:

1. Suggested questions for students when viewing the clip:

1. Lightning Rods and Lightning Safety

a. What is the purpose of a lightning rod?

b. How does a lightning rod work? How large is its range of protection? Is there an advantage to having multiple lightning rods?

c. Are you safe from lightning in a car? In a plane?

2. The Nature of Lightning

a. How does lightning propagate? What are the steps involved in the initiation of a lightning channel?

b. Approximately how much charge is in one lightning strike? How much current is conducted to the surface of the earth?

c. Globally, how many thunderstorms occur at one time? How much power is produced? Is this power usable?

d. Where does most lightning occur (e.g., land or water)?

e. Where does most lightning occur in the United States? Why is this particular local conducive to lightning formation?

3. The Connection Between Lightning and Thunder

a. What causes thunder? Answer in terms of pressure and expansion.

b. Can thunder occur without lightning and vice versa?

c. How can you calculate how close a lightning strike is to you?

4. Cloud Electrification (For advanced students).

Students can investigate the current hypothesis regarding cloud electrification. Why has no hypothesis completely explained cloud electrification?