The nuclei of large atoms, such as uranium, with 92 protons, can be modeled as spherically symmetric spheres of charge. the radius of the uranium nucleus is approximately 7.4×10−15m . part a what is the electric field this nucleus produces just outside its surface? express your answer using two significant figures.

Total number of Photons = 92. 
Radius of the Nucleus = 7.4 x 10^-15 m 
Charge of the nucleus = 1.6*10^-19. 
Total charge q = 92 x 1.6*10^-19 = 147.2 x 10^-19 
k = 9 x 10^9 N m^2 / C^2 
Electric field charge E = kq / r^2 
=> E = (9 x 10^9 x 147.2 x 10^-19) / (7.4 x 10^-15) ^2  
=> (1324.8 x 10^-10) / 54.76 x 10^-30 => 24.19 x 10^20 N/C

The formula for the electric field is written below:

E = kQ/d²
where
k is the Coulomb's Law constant = 9×10⁹ N
Q is the total charge
d is the distance of the object from the center

The charge of each proton is +1.6×10⁻¹⁹ C. So,
Q = 92(+1.6×10⁻¹⁹ C) = 1.472×10⁻¹⁷ C
So,

E = (9×10⁹ N)(1.472×10⁻¹⁷ C)/(7.4×10⁻¹⁵m)²
E = 2.42×10²¹ N/C