A thin metallic shell of radius 40 cm has a charge of -25 nC on it.At the center of the sphere is a point charge of 35 nC.What is the electric field 15 cm from the center of the shell? A) 2.4 $\times$ 10⁴ N/C inward B) 1.4 $\times$ 10⁴ N/C inward C) 2.4 $\times$ 10⁴ N/C outward D) 1.4 $\times$ 10⁴ N/C outward E) 4.0 $\times$ 10⁴ N/C outward

Question

Quizplus · Accepted Answer

By Gauss's law, the electric field inside a conducting shell is zero. Therefore, the electric field at the point 15 cm from the center of the shell is due only to the point charge. 
Using the formula for the electric field due to a point charge, we have: 
E = k(Q/r^2) 
where k is the Coulomb constant, Q is the charge on the point charge, and r is the distance from the point charge. 
Plugging in the values, we get: 
E = (9 x 10^9 N*m^2/C^2)(35 x 10^-9 C)/(0.15 m)^2 
E = 1.4 x 10^14 N/C 
The electric field is directed outward, away from the point charge. Therefore, the correct answer is D.

A Thin Metallic Shell of Radius 40 Cm Has a Charge