Calculating Electric Field Strength of a Charged Metal Sphere

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SUMMARY

The discussion focuses on calculating the electric field strength of a charged metal sphere with a diameter of 10 cm and a surface charge density of 1.09085 x 1018 electrons/cm2. The correct formula to use is E = k x Q/r2, where k is Coulomb's constant (9.0 x 109 N m2/C2). The electric field strength at a distance of 25 cm from the surface of the sphere is determined to be 5.5 x 1012 N/C, requiring the distance to be measured from the center of the sphere, not the surface.

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Matticus9
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Homework Statement


A metal sphere with a diameter of 10 cm has a charge distribution of 1.09085 x 1018 electrons/cm2 on its surface. What is the electric field strength at a distance of 25 cm from the surface of the sphere? (Answer: 5.5 x 1012 N/C)

Homework Equations


I wasn't given any equations. Only ones I know are
E= F/q= (kqQ/r2)/q
E= k x Q/r2

The Attempt at a Solution


E= (k x Q)/r2= 9.0 x 109 x Q/ 25 cm2= ?
 
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Hi Matticus9, Welcome to Physics Forums.

Your expression for E is not well thought out. The problem statement says that the distance of 25 cm is from the surface of the sphere, not its center. The distance in the formula should be the distance from the center.

What can you do to find the total charge Q on the surface of the sphere? You might need to dig into your geometry knowledge to add some equations to your relevant equation list.
 
I still don't understand.
 

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