# Electric Field strength of sphere

• james6008
In summary, a solid sphere with a radius of 3 cm and a charge of +4 uC has an electric field strength of 0 N/C at any point inside the sphere due to electrostatic shielding. If the charge is placed inside the sphere, the relevant equation to calculate the electric field strength is E = Q/(4pi eo r^2), where r is the distance between the charge and the point at which the electric field is being calculated. The value of r must be in meters, with 0.03m being the radius of the sphere and 0.014m being the distance from the center to the point.

#### james6008

Hi everyone

I just need some help with this question. Its a simple one I'm pretty sure.

## Homework Statement

A solid sphere of radius 3 cm is made from a conductor and has a charge of
+ 4 uC placed upon it. What is the electric field strength 1 mm from the
centre of the sphere?

## Homework Equations

I think this is relevant equation to this.

E = Q/(4pi eo r^2)

## The Attempt at a Solution

Q is (4 X 10^-6)/ ( 4 * pi * (8.8 * 10^-12) * (r^2) )

I am a bit confused about r. Is r just the radius in meter which will be 0.03m or do I have to include 1mm from the center in that case it would be 0.014m?

Thanks

well if the charge was placed on the outer surface then
no electric field inside at any point
due to electrostatic shielding
in case it is placed inside, then r is the distance of the straight line joining the charge and the point at which to calculate the electric field
again that point must lie inside in the case

## 1. What is the formula for calculating the electric field strength of a sphere?

The formula for calculating the electric field strength of a sphere is E = kQ / r^2, where E is the electric field strength, k is Coulomb's constant (9 x 10^9 N.m^2/C^2), Q is the charge of the sphere, and r is the distance from the center of the sphere.

## 2. How does the electric field strength of a sphere vary with distance?

The electric field strength of a sphere varies inversely with the square of the distance from the center of the sphere. This means that as the distance increases, the electric field strength decreases.

## 3. Can the electric field strength of a sphere ever be negative?

No, the electric field strength of a sphere cannot be negative. It is always a positive value, indicating the direction of the electric field.

## 4. How does the charge of a sphere affect its electric field strength?

The electric field strength of a sphere is directly proportional to its charge. This means that as the charge of the sphere increases, the electric field strength also increases.

## 5. Is the electric field strength of a sphere affected by the material it is made of?

No, the electric field strength of a sphere is not affected by the material it is made of. It depends only on the charge of the sphere and the distance from the center of the sphere.

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