Spherical conducting shell enclosing a non-conducting core

  • Thread starter Thread starter hmparticle9
  • Start date Start date
  • Tags Tags
    Electrostatic
AI Thread Summary
In the discussion about a spherical conducting shell enclosing a non-conducting core, it is established that the charge inside the outer shell arranges itself to neutralize the enclosed charge as much as possible. For the region between the inner boundary and outer shell, the electric field is zero due to the properties of conductors. When considering a scenario with less charge than expected on the outer shell, the electric field can be calculated using Gauss's law, which indicates that the electric field depends on the difference between the total charge and the charge accumulated at the inner boundary. The direction of the electric field within the conductor is clarified, emphasizing that it must be zero because conductors are equipotential. This leads to a deeper understanding of how electric fields behave in such configurations.
hmparticle9
Messages
151
Reaction score
26
Homework Statement
A solid non-conducting sphere of uniform charge density and total charge ##-Q## and radius ##a## is surrounded by a concentric conducting spherical shell of inner radius ##b## and outer radius ##c## with ##a < b < c##. The outer shell has charge##2Q##. I am interested in the case ##r \in [b,c]##
Relevant Equations
$$\int_S \mathbf{E} \cdot d \mathbf{S} = \frac{q}{\epsilon_0}$$
The case I am interested in is ##r \in [b,c]##. Because the outer shell is conducting and the outer shell encloses a charge ##-Q## would it be correct to say that for the case ##r \in [b,c)## the charge inside the outer shell arranges itself in a way to "cancel" as much of the contained charge as it can.

Because the outer shell has ##2Q## to play with we are okay. ##Q## of the ##2Q## charge arranges itself on the shell boundary ##r = b##, hence ##E(r) = 0, r \in [b,c)##.

Am I correct in saying that the remaining charge ##Q## arranges on the outer shell ##r=c##? When we use Gauss's law we obtain
$$E(c) = \frac{Q}{4 \pi \epsilon_0 c^2}$$

If we had less than ##Q## charge in the outer shell I am trying to figure out what ##E(r)## would look like in the outer shell...
 
Last edited:
Physics news on Phys.org
Start by considering what the electric field is at ##b<r<c##, i.e. inside the conducting material. What does Gauss's law have to say about that?
 
Surely the charge ##\hat{Q} < Q## would accumulate at ##r = b##. Gauss's law would say

$$\int_S \mathbf{E} \cdot d \mathbf{S} = \frac{Q - \hat{Q}}{\epsilon_0}$$ within the shell?
 
Last edited:
hmparticle9 said:
Surely the charge ##\hat{Q} < Q## would accumulate at ##r = b##. Gauss's law would say

$$\int_S \mathbf{E} \cdot d \mathbf{S} = \frac{Q - \hat{Q}}{\epsilon_0}$$ within the shell?
Sure, but you didn't answer my question. What is the value of ##\mathbf E## on the left-hand side of the equation? Hint: Under static conditions, a conductor is an equipotential.
 
Sorry ! :)

$$\int_S \mathbf{E} \cdot \text{d} \mathbf{S} = E(r) 4 \pi r^2 = \frac{Q - \hat{Q}}{\epsilon_0} \implies E(r) = \frac{Q - \hat{Q}}{4\pi r^2\epsilon_0}$$
 
hmparticle9 said:
Sorry ! :)

$$\int_S \mathbf{E} \cdot \text{d} \mathbf{S} = E(r) 4 \pi r^2 = \frac{Q - \hat{Q}}{\epsilon_0} \implies E(r) = \frac{Q - \hat{Q}}{4\pi r^2\epsilon_0}$$
That is not correct.

What is the direction of the electric field inside the conductor? Remember that electric field lines point from regions of high electric potential to regions of low electric potential and that conductors are equipotentials. Put it together and come up with a numerical value for the normal component of the electric field on the surface of the Gaussian surface inside the conductor.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Thread 'Trying to understand the logic behind adding vectors with an angle between them'
My initial calculation was to subtract V1 from V2 to show that from the perspective of the second aircraft the first one is -300km/h. So i checked with ChatGPT and it said I cant just subtract them because I have an angle between them. So I dont understand the reasoning of it. Like why should a velocity be dependent on an angle? I was thinking about how it would look like if the planes where parallel to each other, and then how it look like if one is turning away and I dont see it. Since...
Thread 'Correct statement about a reservoir with an outlet pipe'
The answer to this question is statements (ii) and (iv) are correct. (i) This is FALSE because the speed of water in the tap is greater than speed at the water surface (ii) I don't even understand this statement. What does the "seal" part have to do with water flowing out? Won't the water still flow out through the tap until the tank is empty whether the reservoir is sealed or not? (iii) In my opinion, this statement would be correct. Increasing the gravitational potential energy of the...
Back
Top