UNIT - 1
ELECTROSTATICS
2025
1. (a)
What is the effect on capacitance of a parallel plate capacitor if the distance
between its plates is increased?
(b) How will capacitance of a
capacitor change if a dielectric slab is introduced between its plates?
2. In
case of a short electric dipole:
(i)
What is the locus of a point having zero
potential?
(ii)
If electric field intensity at a point in
axial position is E1 and at an equidistant point in equatorial position is E2,
what is the ratio E1/E2.
3. An
infinite plane metallic sheet having surface charge density ‘+σ’ is placed in
vacuum. P is a point at a small distance ‘r’ to its right.
(i)
Write an expression for intensity of
electric field at point P.
(ii)
Now, an identical charged sheet having
surface charge density ‘−σ’ is placed parallel to the first sheet such that the
point P is to its left at the same distance ‘r’. (The point P lies between the
two plates.) (a) What is the resultant intensity of electric field at point P?
(b)
What is its direction?
2024
4. In
an electric dipole, what is the locus of a point having zero potential?
5. A
hollow sphere of radius R has a point charge q at its centre. Electric flux
emanating from the sphere is X. How will the electric flux change, if at all,
when
(a) Radius of the sphere is doubled?
(b) Charge q is replaced by an
electric dipole?
6. In
case of an infinite line charge, how does intensity of electric field at a
point change, if at all, when
(a) Charge on it is doubled?
(b) Distance of the point is halved?
7. What
is meant by the statement “Relative permittivity of water is 81”?
8. Can
a body be given a charge of 2.2 × 10-19 C? Give a reason for your
answer.
9. Obtain
an expression for equivalent capacitance C when three capacitors C1, C2 and C3
are connected in series.
2023
10. A hollow sphere of radius R has a point charge
Q at its centre. Electric flux emanating from it is j. If both the charge and
the radius -of the sphere be doubled, electric flux emanating from the sphere
will:
(a) remain
the same. (c) become 4j (b) become 2j (d) become 8j
11. What
is meant by an equipotential surface?
12. Calculate
equivalent capacitance of the circuit shown in Figure 1 given below:
13. Calculate
electric potential at a point P which is at a distance of 9 cm from a point
charge of 50 μC.
14. Show
that intensity of electric field at a point in broadside position of an
electric dipole is given by:
2022 SEM I
15. The
force between two-point charges separated by a certain distance in air is F. If
each of the two charges be halved and the distance between them be also halved,
the new force would be:
(a) F (b) 2F (c) 3F (d)
4F
16. Which
one of the following is not a property of electric lines of force?
(a) They originate at the positive
charge.
(b) They terminate at the negative
charge.
(c) They intersect each other.
(d) A tangent drawn to a line of
force gives the direction of electric field intensity at the that point.40.
17. Electric
potential at a point on the axial line of a short electric dipole is
(a) directly proportional to
distance.
(b) inversely proportional to
distance.
(c) inversely proportional to square
of the distance.
(d) directly proportional to square
of the distance.
18. The
electric flux emanating from a sphere of radius 2m is j. If radius of the
sphere be made four times, without changing the charge enclosed, electric flux
would
(a) Become
(j/4) (b) Become (j/2) (c) Become (2j) (d) Become (j)
19. An
electric dipole consists of two-point charges +2mC and –2mC separated by a
distance of 4 cm. It is kept at an angle of 30° with an electric field of
intensity of 1 × 105 NC–1. The torque experienced by the
dipole is:
(a) 1 Nm (b) 2 Nm (c) 3 Nm (d) 4 Nm
20. Three-point
charges Q, Q and q are kept at the vertices A, B and C respectively of an
equilateral triangle ABC having each side equal to a. Electrostatic potential
energy of the system is zero. This is possible if q is equal to:
(a) Q (b)
Q/2 (c) –Q/2 (d) –Q/4
21. Consider a point P on the perpendicular
bisector of an electric dipole. At point P,
(a) Electric field is zero.
(b) Electric potential is zero.
(c) Electric field is perpendicular
to the axis of the dipole.
(d) Potential gradient is zero
22. Consider
10 identical capacitors each of capacitance 5 μF. The ratio of the minimum and
the maximum possible values of the capacitance that can be obtained from them,
is:
(a) 1 : 50 (b) 1 : 100 (c) 50 : 1 (d) 100 : 1
23. The
capacitance of a parallel plate capacitor does not depend on
(a) area of each plate.
(b) potential difference between the
two plates.
(c) nature of the medium between the
two plates.
(d) distance between the two plates.
24. The
surface charge density of large conducting sheet is 17.7 × 10–6 cm–2.
The electric field intensity at a point just outside the sheet is:
(a) 1 × 104 NC–1
(b) 5 × 104 NC–1 (c) 1 × 105 NC–1
(d) 1 × 106 NC-1
2020
25. A
point charge 'q' is kept at each of the vertices of an equilateral triangle
having each side 'a'. Total electrostatic potential energy of the system is :
26. State
Gauss' theorem
27. Show
that intensity of electric field E at a point in broadside on position is given
by:
where the terms have their usual
meaning.
28. A
parallel plate capacitor is charged by a battery, which is then disconnected.
A
dielectric slab having dielectric constant (relative permittivity) K, is now
introduced between its two plates in order to occupy the space completely.
State in terms of K its effect on the following:
(i)
The capacitance of the capacitor.
(ii)
The potential difference between its
plates.
(iii)
The energy stored in the capacitor.
2019
29. A
closed surface in vacuum encloses charges −q and +3q. The total electric flux
emerging out of the surface is:
30. (i)
Define equipotential surface.
(iii)
Calculate the net emf across A and B shown
in Figure 1 below:
31. Obtain
an expression for electric potential ‘V’ at a point in an end-on position i.e.,
axial position of an electric dipole.
32. Three
capacitors of capacitance C1 = 3 μF,C2 = 6μ Fand C3 = 10 μF, are connected to a
10 V battery as shown in Figure below
Calculate:
(a) Equivalent capacitance.
(b) Electrostatic potential energy
stored in the system.
2018
33. Deduce
an expression for equivalent capacitance C when three capacitors C1, C2 and C3
are connected in parallel.
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