Question

15.10 At what distance away from a 5 μC point charge is the electric field equal to 2.6 x 106 N/C?

15.11 Find the electric field of a 7 μC point charge at each distance: a) 10 cm away, b) 25 cm away, and c) 75 cm away.

Answer 1

Given

15.10

point charge q = 5*10^-6 C

Electric field E = 2.6*10^6 N/C

we know that the field is E = kq/r^2

2.6*10^6 = 9*10^9*5*10^-6 /(r^2)

solving for r , r = 0.131558 m

15.11

charge q = 7*10^-6 C

distance r = 10 cm = 0.1 m

we know that the field of a charge q at a distance r is E = kq/r^2

E = 9*10^9*5*10^-6 /(0.1^2) N/C

E = 4500000 N/C

at r = 25 cm = 0.25 m

E = kq/r^2

E = 9*10^9*5*10^-6 /(0.25^2) N/C

E = 720000 N/C

at r = 75 cm = 0.75 m

E = kq/r^2

E = 9*10^9*5*10^-6 /(0.75^2) N/C

E = 80000 N/C