Unveiling Invisible Forces: The Magic of Static Electricity & the Electroscope!

I’m Ken Kuwako, your Science Trainer! Every day is an experiment!

That “Zap!” you feel when you touch a doorknob in winter, or the “Crackle, crackle…” when you take off a sweater – everyone’s experienced static electricity. It’s such a common phenomenon, isn’t it? But its true nature is invisible, almost like capricious magic.

What if you could harness that unseen force and witness its magic with your own eyes?

Today, I’m thrilled to introduce a captivating science experiment using a magical box that makes this dream come true: the electroscope! All you need to prepare are balloons and plastic sheets. Welcome to the magical world of science!

Watch the video below!

Just by bringing a charged object close, the metal leaves instantly spring open, just like in the video!Doesn’t it feel like the balloon has turned into a magic wand?

The “why?” hidden within this simple phenomenon is the perfect gateway into the world of science.

Now, let’s unveil the secret behind this magic—or rather, this scientific mystery—together!

So, what exactly is “Static Electricity”?

Before we delve into the mystery of why the leaves open, let’s talk a little about the true nature of static electricity.

Everything around us is made of tiny particles called “atoms.” Inside these atoms are “protons” that carry a positive charge and “electrons” that carry a negative charge. Normally, the amounts of positive and negative charges are balanced, making the atom electrically neutral.

However, when objects rub against each other, like rubbing a balloon with cloth, electrons can sometimes transfer from one object to another. This excess or deficit of electrons is what causes static electricity. Ancient Greeks knew that rubbing amber (which means “ēlektron” in Greek, the origin of the word “electricity”) would attract feathers.

Why Do the Leaves Open? Following the Invisible Dance of Electrons!

Now, let’s finally unravel the mystery of the electroscope.

Case 1: Approaching with a Positive Charge…

First, consider a silk cloth that has been rubbed with a balloon. This cloth actually loses electrons to the balloon, becoming positively charged.

When you bring this positively charged silk near the metal disk of the electroscope, the free-moving electrons (negative charges) inside the metal exclaim, “Yay, positive!” and are drawn towards the disk. This phenomenon is called “electrostatic induction.”

As a result, the leaves at the bottom are left with a deficit of electrons, becoming positively charged. As you know, like charges (positive-positive, negative-negative) repel each other. So, the two leaves push each other away, shouting “Get away!” and magnificently spread apart.

Case 2: Approaching with a Negative Charge…

Next, let’s try bringing a balloon that has received electrons and is negatively charged (the opposite of the silk) close to the electroscope.

This time, startled by the approaching negative charge on the disk, the electrons within the metal exclaim, “Whoa, negative is here!” and rush down towards the leaves.

Consequently, the leaves become saturated with negative charges. Since negative charges also repel each other, the leaves again spread open. Even though both cases result in the “opening” phenomenon, the electron drama unfolding within is completely different!

Quick Fact: What Happens if You Bring a Magnet Close?

No reaction to a magnet

By the way, if you bring a magnet near, the leaves won’t react at all. This shows that the force of static electricity (electric force) and the force of magnets (magnetic force) are different in nature. The electroscope, as its name suggests, is an excellent detective that detects only static electricity.

Control the Leaves with a Single Fingertip! The Mystery of Grounding

Now, here’s where the experiment gets really interesting. With the negatively charged balloon brought close, making the leaves open, gently touch the top disk with your finger.

The leaves close when touched.

Amazingly, the leaves that were repelling each other instantly close! What just happened?

In fact, the large number of electrons that had fled to the leaves escaped through your body to the ground. Our bodies and the Earth act as enormous escape routes (or sources) for electricity. This is called “grounding.” Since the electrons left through your body, the leaves returned to an electrically neutral state and closed.

And now for the climax. Remove your finger from the disk, and then move the balloon away…

When the balloon is pulled away…

This time, the leaves remain open!

Astonishingly, the leaves now remain open! What could this mean?

Let’s look at the model diagram.

After you touch the electroscope and electrons escape, at the moment you remove your finger, the entire electroscope is electron-deficient (in a positive state). However, because the negatively charged balloon is still nearby, the remaining electrons are attracted to the disk.

Now, when you move the balloon, which was attracting the electrons, away…

The positive charges that were gathered on the disk spread evenly throughout the entire electroscope. As a result, the leaves also become positively charged and repel each other again, opening up. This time, we successfully charged the electroscope itself with positive electricity! Isn’t that fascinating?

Now, if you performed the same operation with the initially positively charged silk cloth, could you charge the entire electroscope negatively? Please try to imagine this mysterious movement of electrons and give it a try!

A more detailed explanation is also available in this video. Please check it out.

・Print (Electroscope)

Even more exciting experiments with a static electricity generator (Van de Graaff)!

If you want to experience even more powerful static electricity, we recommend experiments using the Van de Graaff generator! This device is actually an incredible machine, once used in nuclear research as a type of particle accelerator.

This experiment also includes one conducted on a TV show with Suzu Hirose, Ryohei Suzuki, Yasuko, and Chocolate Planet’s Osada and Matsuo.Click here for details.

【科学監修】ビリビリ電気賞状!?広瀬すずさんと体験した静電気実験授業（沸騰ワード１０）

※ Please ensure that experiments using the static electricity generator (Van de Graaff) are always conducted under the supervision of a specialist. Please proceed with caution. For requests regarding static electricity experiments (e.g., experiment classes, TV supervision/appearances, etc.), please contact us here.

【Special Feature】You won’t be able to stop! Static Electricity Experiments

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