Problem related to two conductors in contact

[gracy]

Homework Statement

An isolated conducting spherical shell carries a negative charge. What will happen if a positively charged metal object is placed in contact with the shell interior? Discuss the three cases in which the positive charge is a) less than , b) equal to, and c) greater than the negative charge in magnitude

Homework Equations

Important point:
The net electric charge of a conductor resides entirely on its surface.

The Attempt at a Solution

I want to know
charged metal object is placed in contact with
what does it mean?
Does it mean charged metal object is placed inside the shell interior?

Is it correct?

 

[Simon Bridge]

When something is placed in contact with something else it means the two things are touching each other.

 

[gracy]

You mean conductor touches another conductor's interior?by?How would the setup look like?

 

[NascentOxygen]

It would look like a pair of 3 dimensional bodies as represented in your 2D sketch. Imagine a small metal egg held inside a larger hollow metal shell so that there is air all around the smaller one, insulating it. Then allow the middle one to fall onto the interior surface of the larger one when you want them to contact.

 

[gracy]

. Then allow the middle one

Did not understand this .

 

[ehild]

Object in contact with the shell interior:

 

[gracy]

I want to know
charged metal object is placed in contact with
what does it mean?
Does it mean charged metal object is placed inside the shell interior?

@ehild diagram you drew greatly explained my doubt.
Now ,could you please do one more favor?
Can't we include charges in that particular figure?

 

[gracy]

Is it right ?
I am not showing that Q>q or any such thing.I am just considering the general case.
Just want to know/confirm location of charges whatever the magnitude may be .

 

[Chestermiller]

After the conductors have been put in contact in contact with one another, those will no longer be the charges on them.

 

[gracy]

those will no longer be the charges on them.

You meant those will no longer bear the charges on them,right?

 

[gracy]

After the conductors have been put in contact with one another, those will no longer be the charges on them.

Can you please tell the reason?

 

[Chestermiller]

Can you please tell the reason?

What are your thoughts on this?

 

[gracy]

I am unable to comprehend this.
As I wrote

I am not showing that Q>q or any such thing

How can we cancel them?

 

[haruspex]

Can you please tell the reason?

The charges will be redistributed. What facts do you know about the distribution of charge on a conductor?

 

[Chestermiller]

How can we cancel them?

Gracy, here's a multiple choice quiz for you:
1. In a conductor, positive and negative charges are regarded as (a) mobile or (b) not mobile?
2. Positive and negative charges (a) attract or (b) repel?
3. If two conductors are brought into contact with one another, charges can (a) freely pass between them or (b) not freely pass between them?
4. If a positive and a negative charge are allowed to come into contact, they (a) neutralize each other or (b) don't neutralize each other?

 

[gracy]

In a conductor,positive and negative charges are regarded as (a) mobile or (b) not mobile?

In a conductor
positive charges - not mobile
Negative charges-mobile

Positive and negative charges (a) attract or (b) repel?

Positive and negative charges attract each other.

If two conductors are brought into contact with one another, charges can (a) freely pass between them or (b) not freely pass between them?

Before answering this I want to know one thing,are these conductors neutral?

 

[gracy]

If a positive and a negative charge are allowed to come into contact, they (a) neutralize each other or (b) don't neutralize each other?

neutralize each other

 

[Chestermiller]

In a conductor
positive charges - not mobile

In my question, I was careful to use the words "are regarded as." Positive charges are just a deficit of electrons, so, if electrons can move in one direction, isn't that the same as positive charges moving in the opposite direction. If positive charges are not mobile, how come, when a conductor is charged positively, all the positive charges migrate to the outer surface of the conductor?

Before answering this I want to know one thing,are these conductors neutral?

If the conductors were neutral, there could not be a net migration of charge between them. So, what if they were not neutral to begin with?

 

[gracy]

isn't that the same as positive charges moving in the opposite direction

I thought by positive charge you meant proton.That's why I said not mobile.

 

[gracy]

If two conductors are brought into contact with one another, charges can (a) freely pass between them or (b) not freely pass between them?

what if they were not neutral to begin with?345636"][./QUOTE]
charges can freely pass between them

 

[gracy]

Previous post went all wrong.sorry

If a positive and a negative charge are allowed to come into contact, they (a) neutralize each other or (b) don't neutralize each other?

They neutralize each other

 

[Chestermiller]

I thought by positive charge you meant proton.That's why I said not mobile.

Even if a conductor has atoms within it that are positively charged because they had lost electrons, electrons can migrate to them from adjacent neutral atoms to neutralize the charge, while the adjacent atoms then become positively charged. Certainly this constitutes mobility of positive charge.

 

[Chestermiller]

Previous post went all wrong.sorryThey neutralize each other

The question was "If two conductors are brought into contact with one another, charges can (a) freely pass between them or (b) not freely pass between them?" The question was not "what will ultimately happen." And, if the charges on the two conductors were not equal and identical in sign to begin with, they certainly will not ultimately fully neutralize.

 

[gracy]

If two conductors are brought into contact with one another,charges can (a) freely pass between them or (b) not freely pass between them

Charges can freely pass between them.

 

[Chestermiller]

So now, based on the answers to these four questions, how would you analyze the original problem at hand?

Chet

 

[gracy]

Will net charge come on the outer surface of the spherical shell?

 

[gracy]

Will net charge come on the outer surface of the spherical shell?

I am asking this for a reason,actually my book gives this as a hint.

 

[Chestermiller]

Will net charge come on the outer surface of the spherical shell?

Yes.

 

[gracy]

I am hesitant ,but could you please explain why net charge will come on the outer surface of the spherical shell?By giving hints or multiple choice questions.

 

[Chestermiller]

I am hesitant ,but could you please explain why net charge will come on the outer surface of the spherical shell?By giving hints or multiple choice questions.

By net charge, we mean that all the charges that are left are either positive or negative, because the other charges have neutralized one another, correct? If you have all charges of one sign, are they going to attract one another, or are they going to get as far from each other as possible?

Chet

 

[gracy]

are they going to get as far from each other as possible?

They are going to get as far from each other as possible.
But why on the outer surface of the spherical shell not on the small conductor?

 

[Chestermiller]

They are going to get as far from each other as possible.
But why on the outer surface of the spherical shell not on the small conductor?

Because they can migrate from the small conductor to the spherical shell, and thereby get further apart.