Quick Physics: Electroscope - how it works.

Summary

In this video, Paul explains the working of an electroscope and how it demonstrates the principle of conservation of charge. Using a perspex rod and silk, he shows how rubbing the two objects causes electrons to transfer, creating a charge. By bringing the charged rod near the electroscope, the needle deflects as a result of the redistribution of electrons in the metal plate. Paul further demonstrates how the needle can stay deflected by removing electrons from the electroscope or neutralizing it through contact with the ground. The video emphasizes that charge is conserved, only transferred between objects.

Takeaways

• 😀 The electroscope is used to demonstrate the conservation of charge.
• 😀 Rubbing a perspex rod with silk transfers electrons, causing the perspex rod to become positively charged.
• 😀 Conservation of charge means no electrons are lost, only transferred between objects.
• 😀 When a charged perspex rod is brought near an electroscope, the needle moves due to electron movement in the metal plate.
• 😀 The electroscope needle moves because of repulsion between positively charged metal parts.
• 😀 Once the perspex rod is removed, the electrons return to their original positions, and the electroscope returns to normal.
• 😀 By attaching the perspex rod to the electroscope, the needle stays deflected, demonstrating the charge transfer.
• 😀 The electroscope needle stays repelled when electrons are transferred to the perspex rod, leaving the electroscope with a positive charge.
• 😀 Touching the electroscope allows electrons from the ground to neutralize the charge, causing the needle to return to its neutral position.
• 😀 The strength of the charge influences how far the electroscope needle deflects, illustrating the relationship between charge and deflection.
• 😀 Overall, the video demonstrates that charge is conserved during these processes, with no loss of electrons, just transfers.

Q & A

What is the purpose of the electroscope in this experiment?

The electroscope is used to detect the presence of electric charge and to demonstrate how charge transfers from one object to another, based on the movement of its needle when influenced by an external charge.

How does rubbing the perspex rod with silk affect the charge on the rod?

Rubbing the perspex rod with silk transfers electrons from the perspex to the silk, causing the perspex rod to become positively charged and the silk to become negatively charged.

What is meant by 'conservation of charge' in this context?

Conservation of charge means that electrons are not created or destroyed in the process. They are simply transferred between objects, like from the perspex rod to the silk or the electroscope.

Why does the needle of the electroscope move when the charged perspex rod is brought near it?

When the charged perspex rod is brought near the electroscope, it causes electrons in the metal plate to either be attracted or repelled, resulting in a redistribution of charges and causing the needle to move as a result of the repulsion of like charges.

What happens to the electroscope needle when the perspex rod is removed?

When the perspex rod is removed, the electrons that were attracted to the top of the electroscope plate return to their original positions, and the needle of the electroscope moves back to its neutral position.

How does the electroscope remain in the 'repelled' position after the perspex rod is moved away?

The electroscope remains in the repelled position if some electrons are removed from the electroscope by touching it with the perspex rod, which leads to a net positive charge, keeping the two metal pieces repelled.

What happens when a person touches the electroscope?

When a person touches the electroscope, electrons from the ground (through the person’s body) neutralize the charge on the electroscope, causing the needle to return to its neutral position.

What role does the metal connection in the electroscope play?

The metal connection in the electroscope allows the transfer of electrons to and from the metal plate, which in turn affects the movement of the needle in response to nearby charges.

Why does the electroscope needle move more when a stronger charge is applied?

The electroscope needle moves further when a stronger charge is applied because the increased amount of charge causes a greater repulsion between the two metal pieces, leading to a larger deflection of the needle.

How does the movement of the electroscope needle relate to the principle of conservation of charge?

The movement of the electroscope needle demonstrates the redistribution of charge between the metal plate and the surrounding air, which is consistent with the conservation of charge, as no charge is lost—only transferred.