# Rank charge density of spheres

## Homework Statement

Sphere 1 has net positive charge Sphere 2 has net negative charge Sphere 3 has net positive charge

The ranking of net charge magnitudes are
SPHERE 3 > SPHERE 2 > SPHERE 1

All spheres are conductors

Sphere 2 is moved away from Sphere 1 and toward Sphere 3 so that 2 and 3 touch. Rank the charge density at each labeled point A -- E, greatest first. (Note that point E indicates the left side of Sphere 3; there is no labeled point on the right side of Sphere 3.)

Rank positive charge greater than negative charge. Include zero in your ranking.

HINT: Image what would happen is Sphere 1 were removed; then, consider what effect Sphere 1 has on Spheres 2 and 3 when it is present.

None

## The Attempt at a Solution

Sphere 3 has net positive charge and has the highest magnitude of net charge, sphere 3 is pushing the positives in sphere 2 to point C and since sphere 3 has the most net charge points E and D now have net positive charge, sphere 1 is net positive so it is pushing the positives in sphere 2 towards sphere 3 so I think C, D & E are all positively charged now and all the negative charged has transferred to the right corner of sphere 3. since sphere 1 is net positive I feel A and B are also positively charged

## Answers and Replies

Related Introductory Physics Homework Help News on Phys.org
SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member

## Homework Statement

Sphere 1 has net positive charge Sphere 2 has net negative charge Sphere 3 has net positive charge

The ranking of net charge magnitudes are
SPHERE 3 > SPHERE 2 > SPHERE 1

All spheres are conductors

Sphere 2 is moved away from Sphere 1 and toward Sphere 3 so that 2 and 3 touch.
View attachment 230361

Rank the charge density at each labeled point A -- E, greatest first. (Note that point E indicates the left side of Sphere 3; there is no labeled point on the right side of Sphere 3.)

Rank positive charge greater than negative charge. Include zero in your ranking.

HINT: Image what would happen is Sphere 1 were removed; then, consider what effect Sphere 1 has on Spheres 2 and 3 when it is present.

None

## The Attempt at a Solution

Sphere 3 has net positive charge and has the highest magnitude of net charge, sphere 3 is pushing the positives in sphere 2 to point C and since sphere 3 has the most net charge points E and D now have net positive charge, sphere 1 is net positive so it is pushing the positives in sphere 2 towards sphere 3 so I think C, D & E are all positively charged now and all the negative charged has transferred to the right corner of sphere 3. since sphere 1 is net positive I feel A and B are also positively charged
What were the initial positions of the spheres?

What were the initial positions of the spheres?
initially 2 was in the middle, 1 was far left 3 was far right,
then
2 was touching 1 and was moved away towards 3

Need halp

SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
initially 2 was in the middle, 1 was far left 3 was far right,
then
2 was touching 1 and was moved away towards 3
Seems like this is the tail end of a post which has been either removed from view or deleted.

If that's so, can you at least summarize the results of those parts?

• isukatphysics69
Seems like this is the tail end of a post which has been either removed from view or deleted.

If that's so, can you at least summarize the results of those parts?
Yes, I will be back momentarily with the results

Seems like this is the tail end of a post which has been either removed from view or deleted.

If that's so, can you at least summarize the results of those parts?
Three conducting spheres -- 1, 2, and 3 -- are shown below. Spheres 1 and 2 are initially neutral and Sphere 3 initially has a net positive charge. Spheres 2 and 3 are the same size, but Sphere 1 is larger, as indicated in the diagram. Note also that the center of Sphere 1 is about 10 times farther from the center of Sphere 3 as the radius of Sphere 3. Rank the charge density at each labeled point A -- E, greatest first. Input your answer in the format A>B=0>C>D=E.

Rank positive charge greater than negative charge. Include zero in your ranking.

CORRECT ANSWER : E>C>A>0>B>D

Sphere 2 is moved toward Sphere 1 so that they touch. Rank the magnitude of the net charge on each of the three spheres 1 -- 3 in the previous image, greatest first. Here, magnitude means absolute value, so ignore the sign of the charge.

CORRECT ANSWER: 3>2=1

Rank the charge density at each labeled point A -- E, greatest first. Input your answer in the format A>B=0>C>D=E.

Rank positive charge greater than negative charge. Include zero in your ranking.

CORRECT ANSWER: E>A>B=C=0>D

Sphere 2 is moved away from Sphere 1 and toward Sphere 3 so that 2 and 3 touch. Rank the magnitude of the net charge on each of the three spheres 1 -- 3, greatest first. Here, magnitude means absolute value, so ignore the sign of the charge.

CORRECT ANSWER: 3>2>1

Rank the charge density at each labeled point A -- E, greatest first. (Note that point E indicates the left side of Sphere 3; there is no labeled point on the right side of Sphere 3.)

Rank positive charge greater than negative charge. Include zero in your ranking.

HINT: Image what would happen is Sphere 1 were removed; then, consider what effect Sphere 1 has on Spheres 2 and 3 when it is present.

CORRECT ANSWER: THIS IS WHERE I AM COMPLETELY STUCK

#### Attachments

SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
Three conducting spheres -- 1, 2, and 3 -- are shown below. Spheres 1 and 2 are initially neutral and Sphere 3 initially has a net positive charge. Spheres 2 and 3 are the same size, but Sphere 1 is larger, as indicated in the diagram. Note also that the center of Sphere 1 is about 10 times farther from the center of Sphere 3 as the radius of Sphere 3.
...

Sphere 2 is moved away from Sphere 1 and toward Sphere 3 so that 2 and 3 touch. Rank the magnitude of the net charge on each of the three spheres 1 -- 3, greatest first. Here, magnitude means absolute value, so ignore the sign of the charge.

CORRECT ANSWER: 3>2>1

Rank the charge density at each labeled point A -- E, greatest first. (Note that point E indicates the left side of Sphere 3; there is no labeled point on the right side of Sphere 3.)

Rank positive charge greater than negative charge. Include zero in your ranking.

HINT: Image what would happen is Sphere 1 were removed; then, consider what effect Sphere 1 has on Spheres 2 and 3 when it is present.

CORRECT ANSWER: THIS IS WHERE I AM COMPLETELY STUCK
I'm surprised that the answer given for magnitude in this case is correct. I would have Sphere2 > Sphere3 > Sphere1

Use the hint(s). The first part seems straight forward.

It seems clear to me which point has the greatest (positive) charge density What do you think it may be?

#### Attachments

• isukatphysics69
I'm surprised that the answer given for magnitude in this case is correct. I would have Sphere2 > Sphere3 > Sphere1

Use the hint(s). The first part seems straight forward.

It seems clear to me which point has the greatest (positive) charge density What do you think it may be?
I think E has the greatest charge density

SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
I think E has the greatest charge density
Why is that?

Notice the answers for Spheres 1 and 2 touching?

• isukatphysics69
Why is that?

Notice the answers for Spheres 1 and 2 touching?
I was thinking that E is the greatest because 3 has the greatest net charge and it is a positively charged sphere

My thinking was E>C>B>0>A>D

Sphere 3 has greatest net charge and positive, so it is E with the greatest, then that positive charge is pushing the positives in sphere 2 to the left so C is also positive but now as I am typing this I think B is before C

SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
I was thinking that E is the greatest because 3 has the greatest net charge and it is a positively charged sphere
Yes, but 2 and 5 are touhing and they're conductors. What effect does 1 have on them?

• isukatphysics69
Yes, but 2 and 5 are touhing and they're conductors. What effect does 1 have on them?
1 is polorizing them pushing the positives to the right

So where do the negatives in the net negative sphere 2 go? its so confusing because you have 1 polorizing from the left and 3 polorizing on the right but 3 is more powerful so it should be pushing the positives to C but I don't know what happens to the negatives from 2, do they just go to the right corner of 3?

SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
1 is polarizing them pushing the positives to the right
Oh ! I mis-read the answer to the case of 1 and 2 touching.

• isukatphysics69
SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
My thinking was E>C>B>0>A>D

Sphere 3 has greatest net charge and positive, so it is E with the greatest, then that positive charge is pushing the positives in sphere 2 to the left so C is also positive but now as I am typing this I think B is before C
I doubt that A is negative, likewise doubt that B is positive. The side of Sphere 1 closest to the Spheres 2&3 should have positive (like) charge driven to the far side and negative (unlike) charge attracted.

• isukatphysics69
I doubt that A is negative, likewise doubt that B is positive. The side of Sphere 1 closest to the Spheres 2&3 should have positive (like) charge driven to the far side and negative (unlike) charge attracted.
Im wondering what happens to the negatives from the net negatively charged sphere 2?

Im getting really pissed off at physics right now

SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
Im wondering what happens to the negatives from the net negatively charged sphere 2?
They are neutralized by some of the positive charges which make up the net positive charge of Sphere 3. After all, they're conductor making contact..

• isukatphysics69
Delta2
Homework Helper
Gold Member
Since 2 and 3 touch and have exact same geometry, I expect 2 and 3 to have exact same charges (both positive if understood correctly the previous processes that lead to this setup). But after we examine the effect of sphere 1, 2 will have abit less positive charge and 3 abit more positive charge since the net electric field inside 2 and 3 must cancel the electric field from sphere 1. So indeed it will be 3>2>1 for the charge.

And for the charge densities, it will be C>A>D=E=0>B

• isukatphysics69
They are neutralized by some of the positive charges which make up the net positive charge of Sphere 3. After all, they're conductor making contact..
So my understanding at this time is all of points are positive. My professor told me earlier that the combination of spheres 2 and 3 are not polorizing sphere 1 enough to make point B negative, I was just confused about the contact between them because I don't know how much more sphere 3 is positive than sphere 2 is negative and I didn't know if it was only slightly more it would be able to neutralize

Since 2 and 3 touch and have exact same geometry, I expect 2 and 3 to have exact same charges (both positive if understood correctly the previous processes that lead to this setup). But after we examine the effect of sphere 1, 2 will have abit less positive charge and 3 abit more positive charge since the net electric field inside 2 and 3 must cancel the electric field from sphere 1. So indeed it will be 3>2>1 for the charge.

And for the charge densities, it will be C>A>D=E=0>B
Hey man thank you for your time but please do not tell the answers, that is incorrect but in the future please do not just tell the answer thank you #### Attachments

• Delta2
Delta2
Homework Helper
Gold Member
Ok I am sorry, can you tell me the web page to check myself, I did the mistake of taking B as negative but now I realized this is not the case. (and also D=E=0 doesn't look quite correct ).

• isukatphysics69
Ok I am sorry, can you tell me the web page to check myself, I did the mistake of taking B as negative but now I realized this is not the case. (and also D=E=0 doesn't look quite correct ).
I am logged into my personal moodle account so I cannot share the web page unfortunately