Lightning and Static Electricity

Lesson Plan - Get It!

Audio:

Charged Up!

Clouds may appear quiet and calm, but they are active areas of the atmosphere. Imagine water droplets and ice particles in constant motion inside these clouds. The warm air forces the water and ice to move up, but the gravitational force pulls them down. As a result, they are stuck in the clouds. This compression of billions and billions of water and ice particles constantly moving causes them to bump into each other, which creates electric charges. When the particles are most excited, they produce an enormous discharge that carries a significant amount of electrical energy. This discharge is called a lightning bolt!

• What are electric charges?
• How does static electricity relate to a lightning bolt?

Let us find out by examining the series of screenshots from PhET Interactive Simulations below.

Every object in nature is assumed to be electrically neutral. That is, the number of positive charges present in the object is the same as the number of its negative charges. In the diagram above, the balloon, sweater, and wall are electrically neutral objects.

• What do you think will happen if we rub the balloon on the sweater?

When objects touch or rub against each other, the positive and negative charges interact. The object with high electron affinity, or love for negative charges, will take most of the negative charges and leave the sweater positively charged.

• What will happen if we place the balloon closer to the electrically neutral wall?

When you move the negatively charged balloon close to the electrically neutral wall on the right, it will push the negative charges away. The balloon will then stick to the wall, which is consistent with the rule like charges repel, unlike charges attract – a fundamental principle of static electricity. This means that a positive charge will repel another positive charge but will attract a negative charge.

Discover more about electric charge interactions on your own with this Balloons and Static Electricity interactive simulation from PhET.

• Have you ever been shocked by a doorknob when you reach for it on a cold day?

Let us explore the case of John Travoltage shown in the video below captured from PhET Interactive Simulations.

When John Travoltage rubs the carpet with his foot, excess negative charges build up on his body. When John moved his finger closer to the doorknob, the excess negative charges were transferred to it. Ouch!

The simulation in this video shows how electric charges built up on his body due to its interaction with the carpet. What you saw is an example of static electricity. Electric discharge happens when you create a pathway for the excess charge to pass through. Depending on the type of material, electric discharge can happen really fast...like in a fraction of a second! This means that the "shock" does not stay long, and you will feel it as soon as you reach for the doorknob. Also, the amount of negative charges transferred to the doorknob is not significant enough in number to cause any damage to your body.

Go ahead and test out PhET's John Travoltage yourself!

Lightning Strike

Have you ever heard a crackling sound when you take off your jumper or sweater? When lightning is made in the clouds, the same thing happens, but on a much larger scale!

• How does lightning form?

By now, you know that electrical charges build up in the clouds because of collisions. Lighter, positively-charged particles form at the top of the clouds while heavier, negatively-charged particles sink to the bottom. Meanwhile, the earth is a reservoir of positive and negative charges. When the bottoms of the clouds become negatively charged, they attract positive charges on the earth's surface. Since negative charges are attracted to the positive charges, their attraction will result in a dazzling discharge of energy in the form of lightning strikes!

There are different types of lightning, and the example above is a cloud to ground lightning for obvious reasons. A cloud to cloud lightning happens when the discharge is within separate regions inside the cloud. It begins as an invisible channel of electrically-charged air moving from the cloud toward the ground. When one channel nears an object on the ground, a powerful surge of electricity from the ground moves upward to the clouds and produces the visible lightning strike. This type of lightning is called negative lightning because negative charges are moving from the cloud to the ground.

When you are ready, click NEXT to head over to the Got It? section and practice what you have learned.