Question

(a) Find the voltage (in V) near a 12.6 cm diameter metal sphere that has 8.10 C of excess positive charge on it.

(b) What is unreasonable about this result?

(c) Which assumptions are responsible?

Answer 1

R = 0.126/2 = 0.063 m

v = k*Q/R

=( 9*10^9*8.10) /(0.063) =1.15714286e12 V answer

(b) the voltage value which is obtained above is very high for a small metal sphere

such voltage for a  sphere with radius 6.3 cm is unusual because this sphere will not able to maintain this voltage and will discharge

c)

Which assumptions are responsible?

we can assume that this metal  sphere can have 6.3 cm radius but the charge is very high so assumption about charge is wrong it can't hold that much charge.

let me know in a comment if there is any problem or doubts