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11 Electrostatics
length λ, is given by
V =
λR
2ε 0
1
(z 2 + R 2 ) 1/2
Obtain an expression for the electrostatic field strength as a function of z.
[University of Aberystwyth, Wales 2007]
11.4 (a) Starting from Coulomb’s law, show that the electric potential a distance r
from a point charge q is given by
V =
q
4πε 0 r
(b) Four point charges are assembled as shown in Fig. 11.2. Calculate the
potential energy of this configuration (you may assume that the charges
are isolated and in a perfect vacuum). Does the potential energy depend
upon the order in which the charges are assembled?
(c) Is the charge configuration in (b) stable?
Fig. 11.2
11.5 A spherical liquid drop has a diameter of 2 mm and is given a charge of 2 ×
10 −15 C.
(i) What is the potential at the surface of the drop?
(ii) If two such drops coalesce to form a single drop, what is the potential at
the surface of the drop so formed?
[Indian Institute of Technology 1973]
11.6 A pendulum bob of mass 80 mg carries a charge of 2 × 10 −8 C at rest in a
horizontal uniform electric field of 20,000 V/m. Find the tension in the thread
of the pendulum and the angle it makes with the vertical.
[Indian Institute of Technology 1979]
11.7 An infinite number of charges, each equal to q, are placed along the x-axis at
x = 1, x = 2, x = 4, x = 8, etc. Find the potential and the electric field at the
point x = 0 due to the set of charges.
[Indian Institute of Technology 1974]
11 Electrostatics
length λ, is given by
V =
λR
2ε 0
1
(z 2 + R 2 ) 1/2
Obtain an expression for the electrostatic field strength as a function of z.
[University of Aberystwyth, Wales 2007]
11.4 (a) Starting from Coulomb’s law, show that the electric potential a distance r
from a point charge q is given by
V =
q
4πε 0 r
(b) Four point charges are assembled as shown in Fig. 11.2. Calculate the
potential energy of this configuration (you may assume that the charges
are isolated and in a perfect vacuum). Does the potential energy depend
upon the order in which the charges are assembled?
(c) Is the charge configuration in (b) stable?
Fig. 11.2
11.5 A spherical liquid drop has a diameter of 2 mm and is given a charge of 2 ×
10 −15 C.
(i) What is the potential at the surface of the drop?
(ii) If two such drops coalesce to form a single drop, what is the potential at
the surface of the drop so formed?
[Indian Institute of Technology 1973]
11.6 A pendulum bob of mass 80 mg carries a charge of 2 × 10 −8 C at rest in a
horizontal uniform electric field of 20,000 V/m. Find the tension in the thread
of the pendulum and the angle it makes with the vertical.
[Indian Institute of Technology 1979]
11.7 An infinite number of charges, each equal to q, are placed along the x-axis at
x = 1, x = 2, x = 4, x = 8, etc. Find the potential and the electric field at the
point x = 0 due to the set of charges.
[Indian Institute of Technology 1974]