Electroscope Properties (need explaination)

[lnvoker]

So I came upon this problem on a quiz (didnt count for marks) about my Static Electricity Unit.
It was like... An electroscope is negatively charged, with the leaf at an angle of about 45 degrees. A metal ball on an insulating handle is slowly brought to (but not touching) the plate of the electroscope and the leaf falls. This suggest that the metal ball is...

• uncharged or positively charged
• uncharged or negatively charged
• positively charged
• negatively charged

I put #1 as my answer, but got it wrong since my teacher told the class the it would USUALLY be positive charged and not uncharged.

What I'm confused about is how leaf falls when the metal ball is brought upon the electroscope. The only possibility for it to fall would be if the leaves where both neutral or both + or -. (which i have no idea how this would come)

The question before this was similar, but it stated that: A negatively charged rod is slowly brought near the plate of the electroscope (negatively charged), the leaf... (obviously rises since - repels the electrons to the leaves and - and - repel so the leaves repel.

I just don't get the question after. And I'm somewhat confused how the electrons...charges move in the electroscope.

Help would be appreciated.

Thanks

 

[Delphi51]

The positive rod will attract the negative charge on the electroscope, and that negative charge will move from the leaves to the bulb, leaving less excess charge on the leaves.

You should try a + charged rod close to a neutral electroscope. The rod will induce a charge separation on the electroscope - negative on the bulb and positive on the leaves, causing them to repel.

 

[nlightner]

I can provide an explanation for the properties of an electroscope and how it responds to different charges. An electroscope is a device used to detect and measure electric charge. It consists of a metal rod or plate with a metal leaf attached to the bottom. The metal rod is connected to a conducting wire, which allows it to be connected to a power source or other objects for testing.

When the electroscope is not charged, the metal leaf hangs straight down due to the force of gravity. However, when an electric charge is introduced to the electroscope, the metal leaf becomes charged and is repelled by the like charge on the metal rod. This causes the leaf to move away from the rod and stand at an angle, indicating the presence and type of charge.

In the scenario described, the electroscope is negatively charged and the metal ball is slowly brought near the plate. This causes the electrons in the metal ball to be repelled by the negative charge on the plate, leaving the metal ball with a positive charge. Since opposite charges attract, the positively charged metal ball attracts the negatively charged metal leaf, causing it to fall.

In the second scenario, a negatively charged rod is brought near the negatively charged electroscope. This causes the electrons in the electroscope to repel and spread out, resulting in a decrease in negative charge. This decrease in charge causes the metal leaf to rise, as the negative charge on the rod is now stronger than the negative charge on the electroscope.

It is important to note that these are general principles and the exact behavior of an electroscope may vary depending on factors such as distance, size of charges, and materials used. It is also possible for an electroscope to be uncharged, in which case the metal leaf would remain hanging straight down. I hope this explanation helps clarify the properties and behavior of an electroscope.