Answer:
5.143 kV
Explanation:
Parameters given:
Radius, r = 2 mm = 0.002 m
Charge, Q = 3 * 10^(-6) C
The potential at any point from the center of a sphere is equivalent to the potential from a point charge.
To find Vb - Va, we have to find the potential at point b, Vb, and the potential at point a, Va.
Potential at point b:
Vb = kQ/b
b = 3m
Vb = (9 * 10^9 * 3 * 10^(-6))/3
Vb = (27 * 10³)/3
Vb = 9 kV
Potential at point a:
Va = kQ/a
a = 7m
Va = (9 * 10^9 * 3 * 10^(-6))/7
Va = (27 * 10³)/7
Va = 3.857 kV
Vb - Va = 9 - 3.857
Vb - Va = 5.143 kV