Chapter 11
Electrostatics
Abstract Chapter 11 deals with electrostatics comprising electric field and potential
for various configurations, electric dipole and quadrupole moments, Helmholtz
coils, electrostatic energy, Gauss’ law in integral and differential forms, capacitors,
parallel plates, cylindrical and spherical, various arrangements of capacitors.
11.1 Basic Concepts and Formulae
Coulomb’s law for charges q 1 and q 2 separated by r
F =
1
4πε 0
q 1 q 2
r 2
(Electric force)
(11.1)
ε 0 = 8.85 × 10
−12 C
2
/N/m
2
1
4πε 0
= 9.0 × 10
9 Nm
2
/C
2
Electric field (E) for point charge q at distance r
E =
1
4πε 0
q
r 2
(11.2)
E for a sphere of radius R of uniform charge distribution
E =
1
4πε 0
·
qr
R 2 (r ≤ R)
=
1
4πε 0
·
q
r 2 (r ≥ R)
(11.3)
E for hollow sphere of uniform charge distribution
E = 0 (r < R)
=
1
4πε 0
·
q
r 2 (r > R)
(11.4)
459
Electrostatics
Abstract Chapter 11 deals with electrostatics comprising electric field and potential
for various configurations, electric dipole and quadrupole moments, Helmholtz
coils, electrostatic energy, Gauss’ law in integral and differential forms, capacitors,
parallel plates, cylindrical and spherical, various arrangements of capacitors.
11.1 Basic Concepts and Formulae
Coulomb’s law for charges q 1 and q 2 separated by r
F =
1
4πε 0
q 1 q 2
r 2
(Electric force)
(11.1)
ε 0 = 8.85 × 10
−12 C
2
/N/m
2
1
4πε 0
= 9.0 × 10
9 Nm
2
/C
2
Electric field (E) for point charge q at distance r
E =
1
4πε 0
q
r 2
(11.2)
E for a sphere of radius R of uniform charge distribution
E =
1
4πε 0
·
qr
R 2 (r ≤ R)
=
1
4πε 0
·
q
r 2 (r ≥ R)
(11.3)
E for hollow sphere of uniform charge distribution
E = 0 (r < R)
=
1
4πε 0
·
q
r 2 (r > R)
(11.4)
459