# Finding net charge of a sphere

• mr_coffee
In summary, the conversation discusses an unknown charge on a conducting solid sphere with a radius of 10 cm. The E-field at a distance of 15 cm from the center of the sphere is 3.0E3 N/c and directed radially inward. The net charge on the sphere is calculated using the formula E = q/(4PIEoR^2), with a resulting value of 3.34E-9. However, there is a discrepancy in the calculated answer and it is suggested that the arithmetic may have been done incorrectly. The speaker suggests using the formula E= (kQ)/r^2 to calculate the charge, taking into account that the charge will be negative since the field is directed inward.

#### mr_coffee

An unkown charge sits on a conducting solid sphere of radius 10 cm. If the E-field 15cm from the center of the sphere has the magnitude 3.0E3 N/c and is directed radiually inward, what is the net charge on the sphere? I used
E = q/(4PIEoR^2) plugged and chugged and got 3.34E-9 which isn't right of course, where did i screw up?

Are you sure you're not doing the arithmetic incorrectly? I got a different numeric answer. Post what numbers you used in your calculation.

For an outside point w.r.t the charged solid sphere , the solid sphere behaves like a point charge , so assume solid sphere to be a point charge with charge Q , now electric field at a distance 'r' outide this solid sphere(point charge) is given by:

$E= \frac{kQ}{r^2}$

You just need to fill in the values to calculate Q.Since the field is inwards, the charge will be negative.

BJ

## What is the formula for finding the net charge of a sphere?

The formula for finding the net charge of a sphere is Q = 4πε0R2Φ, where Q is the net charge in Coulombs, ε0 is the permittivity of free space, R is the radius of the sphere in meters, and Φ is the electric flux in volts.

## Can the net charge of a sphere be negative?

Yes, the net charge of a sphere can be negative. This means that the sphere has an overall excess of electrons, giving it a negative charge.

## What factors affect the net charge of a sphere?

The net charge of a sphere is affected by the amount of charge present on the surface of the sphere, the radius of the sphere, and the electric flux passing through the sphere.

## How does the net charge of a sphere affect its electric field?

The net charge of a sphere affects the strength and direction of its electric field. A positive net charge will create an outward electric field, while a negative net charge will create an inward electric field.

## Can the net charge of a sphere be zero?

Yes, the net charge of a sphere can be zero if there is an equal amount of positive and negative charge present on the surface of the sphere, or if the electric flux passing through the sphere is zero.