Expression for Electric Field Outside Sphere

In summary, the question being asked involves a sphere with a charge density that is a function of r, which does not make sense since the sphere is also said to be uniformly charged. The poster is being asked to clarify what they think is intended.
  • #1
eric11201120
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Homework Statement
The charge desnsity within a sphere of radius R is ρ = ρ0 - ar2, where ρ0 and a are constants and r is the distance from the center. Find an expression for a such that the electric field outside the sphere is zero.
Relevant Equations
Electric Field outside a sphere
E = KQ/r2
Electric flux
ΦE=∫EdA
I'm not quite sure where to start. If someone could help me I would very much appreciate it.
 
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  • #2
Hint 1: What does Gauss's law tell you?
Hint 2: Given that expression for charge density, what's the total charge within the sphere?
 
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Steve4Physics said:
But there seems to be a mistake in the question. The sphere can't be both 'uniformly charged' and have a charge density which is a function of r.
Yes, a very sloppily worded question!
 
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1. What is the expression for electric field outside a sphere?

The expression for the electric field outside a sphere is given by E = kQ/r2, where k is the Coulomb's constant, Q is the charge of the sphere, and r is the distance from the center of the sphere to the point where the electric field is being measured.

2. How is the electric field outside a sphere affected by the distance from the center of the sphere?

The electric field outside a sphere is inversely proportional to the square of the distance from the center of the sphere. This means that as the distance increases, the electric field decreases.

3. Is the electric field outside a sphere affected by the charge of the sphere?

Yes, the electric field outside a sphere is directly proportional to the charge of the sphere. This means that as the charge increases, the electric field also increases.

4. Can the expression for electric field outside a sphere be used for both positive and negative charges?

Yes, the expression for electric field outside a sphere is valid for both positive and negative charges. However, the direction of the electric field will be different for positive and negative charges.

5. How does the electric field outside a sphere compare to the electric field inside the sphere?

The electric field outside a sphere is always greater than the electric field inside the sphere. This is because the charge of the sphere is concentrated on the surface, resulting in a stronger electric field at points outside the sphere.

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