# REALLY easy electrostatic question

• Kemilss
In summary, the conversation discusses the confusion of the speaker in understanding the transfer of charge through conduction in non-conductive materials. The answer to a review question on electrostatics seems contradictory to the speaker's understanding, as well as a diploma exam question that shows two electroscopes with different results after being touched by a metal and glass rod. The conversation concludes with a suggestion to read on charging by conduction for a better understanding.
Kemilss
So I'm getting confused by my textbook, and having problems finding any straight forward answers online. I am studying Gr.12 physics myself, so I don't have a teacher. I understand the nature of charges, but somehow I'm getting mixed up when dealing with non-conductive materials. Basically, I don't see how they can actually transfer a charge through conduction. My understanding is that at best they can transfer a charge from the point of contact. To make things worse, I'm doing a review section on electrostatics, and I find something contradictory. Let me explain:

"In each of the following examples, identify the charge on each object and state the method of charging the object"

b) "A glass rod is rubbed with silk and then is touched to a neutral metal sphere"

The answer states: "The glass rod will be positive, the silk will be negative, and the sphere will be
positive. In the rubbing process, the rod and the silk become charged by friction.
When the rod touches the sphere, the sphere becomes similarly positively charged
by conduction"

So I understand that that the glass rod could charge the sphere through induction, but conduction? Either way, I would accept that the glass rod could charge the sphere through conduction, if it wasn't for this other question, which seems to contradict it.

It's a diploma exam question, and it basically shows two electroscopes with their leaves spread. It then says:

"A student touches electroscope I with a neutral metal rod" and then "The student touches electroscope II with a neutral glass rod"

"Which of the following diagrams best shows the leaves of the electroscopes after the electroscopes are touched with the rods"?

The answer is that the electroscope touched by the metal rod has closed leaves (transferred it's charge) and the other electroscope (glass rod) is unchanged ( I assume didn't transfer it's charge )

So I'm trying to understand this, and just when I think I do, I don't!. Can someone perhaps shed some insight and allow me to understand what is really happening?!

Kemilss said:
When the rod touches the sphere, the sphere becomes similarly positively charged
by conduction"
Nah. Charge will not flow from (or to) the insulating rod.

So I understand that that the glass rod could charge the sphere through induction, but conduction? Either way, I would accept that the glass rod could charge the sphere through conduction, if it wasn't for this other question, which seems to contradict it.

It's a diploma exam question, and it basically shows two electroscopes with their leaves spread. It then says:

"A student touches electroscope I with a neutral metal rod" and then "The student touches electroscope II with a neutral glass rod"

"Which of the following diagrams best shows the leaves of the electroscopes after the electroscopes are touched with the rods"?

The answer is that the electroscope touched by the metal rod has closed leaves (transferred it's charge) and the other electroscope (glass rod) is unchanged ( I assume didn't transfer it's charge )
I agree with that.

You might want to read the following to solidify your thinking: Charging by Conduction

1 person

## 1. What is electrostatics?

Electrostatics is the study of electric charges at rest and the forces and fields associated with these charges.

## 2. What is an electric charge?

An electric charge is a fundamental property of matter that can either be positive or negative. Like charges repel each other, while opposite charges attract each other.

## 3. How is electrostatic force calculated?

Electrostatic force is calculated using Coulomb's Law, which states that the force between two charges is directly proportional to the product of the charges and inversely proportional to the distance between them.

## 4. What is an electric field?

An electric field is a region of space around a charged object where a force is exerted on other charged objects. It is represented by electric field lines, which show the direction and strength of the field.

## 5. How does electrostatics apply to everyday life?

Electrostatics plays a role in many everyday phenomena, such as static cling, lightning, and the functioning of electronic devices. It is also studied in industries such as energy, telecommunications, and healthcare.

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