Question

The force of repulsion between two point charges is F, when these are at a distance of 0.1 m apart. Now the point charges are replaced by spheres of radii 5cm having the same charge as that of point charges. The distance between their center is 0.1m, then the force of repulsion will
a) Decrease
b)Increase
c)Remains same

Answer 1

@aaronq

Answer 2

@radar @Cosmichaotic @Abmon98

Answer 3

I just started studying this like yesterday lol but i read that the net charges are on the surface, so they'll be closer together (because of the distance of the radius), so the repulsion force will increase. I'm not 100% on this though

Answer 4

I dont know. @Abmon98 do you know?

Answer 5

But shouldn't they act like point charges ?

Answer 6

i am not sure but decreasing the separation distance increases the force.

Answer 7

Yes, but the answer given is decreases !

Answer 8

I dont see how the force of repulsion would decrease

Answer 9

Also suppose the charge is on the surface, then half the charge will be on A and half will on C, so both the distance will increase and decrease. This should nullify the effect.

Answer 10

True, if it's distributed throughout, then the charge density is less on either side in comparison to the point charge.

Answer 11

So then the force should remain constant or unchanged. Isn't it ?

Answer 12

Hm have you tried using coulombs law to get a quantitative answer?

Answer 13

How should i do that ?
What distance should i take ?

Answer 14

wait if they're 10 cm apart, and the spheres have 5 cm radii, then they are in contact.

Answer 15

Will it affect the repulsive force ?

Answer 16

I honestly dont know, I dont want to give you the wrong answer. My guess is that because they're closer, the repulsion will increase.

Answer 17

Okay...thanx for the help.:)

Answer 18

no problem! hopefully you get this clarified so i can know too haha

Answer 19

The answer given is incorrect !
The force will be unchanged. Contact of the spheres will not affect because the spheres are identical and have equal amount of charge.

Answer 20

are you sure about it ?

Answer 21

yes i am :)

Answer 22

ok.Thank you very much @Abhisar @Abmon98 @aaronq

Answer 23

Interesting! why wouldnt it though?

Answer 24

@aaronq why what ?

Answer 25

Why wouldn't the contact affect the repulsion between them?

Answer 26

\(\color{blue}{\text{Originally Posted by}}\) @Abhisar
The answer given is incorrect !
The force will be unchanged. Contact of the spheres will not affect because the spheres are identical and have equal amount of charge. So no exchange in charge would happen.
\(\color{blue}{\text{End of Quote}}\)

Answer 27

Also the distance between their centers are same as it was between the two point charges. So the force will be constant (by coloumb's law)

Answer 28

So you're saying that regardless of the volume the spheres occupy, we would still treat them as point charges with the charge at the center of the sphere?

Answer 29

Yes i think so. But in reality there is a limitation to this as well. The radius should be small enough in comparison to the distance between the centers.

Answer 30

Okay, thanks for clearing that up!

Answer 31

\(\color{red}{\huge\bigstar}\huge\text{You're Most Welcome! }\color{red}\bigstar\)
\(~~~~~~~~~~~~~~~~~~~~~~~~~~~\color{green}{\huge\ddot\smile}\color{blue}{\huge\ddot\smile}\color{pink}{\huge\ddot\smile}\color{red}{\huge\ddot\smile}\color{yellow}{\huge\ddot\smile}\) @aaronq @iamstark

Answer 32

Hmmm... I just wanted to clear things up. The force would actually decrease because due to repulsion the charges will redistribute to farthest position and thus distance between them would increase which would in turn decrease force.