Worksheet Of Electrostatic
Q1.
If 109 electrons move out of a body to another body every second,
how much time is required to get a
total charge of 1 C on the other body?
Q2. How much
positive and negative charge is there in a cup of water?
Q3. A polythene piece
rubbed with wool is found to have a negative charge of 3 × 10–7 C.
(a) Estimate the number of
electrons transferred (from which to which?) (b) Is there a transfer of mass
from wool to polythene?
Q4. A point charge of 2.0
μC is at the centre of a cubic Gaussian surface 9.0 cm on edge. What is the net
electric flux through the surface?
Q5. An oil drop of 12
excess electrons is held stationary under a constant electric field of
2.55 × 104 NC–1 in
Millikan’s oil drop experiment. The density of the oil is 1.26 g cm–3. Estimate the radius of the drop. (g =
9.81 m s–2; e = 1.60 × 10–19 C).
Q.6 A uniformly charged
conducting sphere of 2.4 m diameter has a surface charge density of 80.0 μC/m2.
(a) Find the charge on the sphere. (b) What is the total electric flux leaving
the surface of the sphere?
Q.7A system has two
charges qA = 2.5 × 10–7 C and qB = –2.5 × 10–7
C located at points
A: (0, 0, –15 cm) and B: (0,0, +15 cm),
respectively. What are the total charge and electric dipole moment of the
system?
Q.8Four point charges qA
= 2 μC, qB = –5 μC, qC = 2 μC, and qD = –5 μC are located
at the corners of a square ABCD of side 10 cm. What is the force on a charge of
1 μC placed at the centre of the square?
Q.9(a) An electrostatic
field line is a continuous curve. That is, a field line cannot have sudden
breaks. Why not? (b) Explain why two field lines never cross each other at any
point?
Q.10 Two point charges qA = 3µC and qB
= –3 µC are located 20 cm apart in vacuum.
(a) What is the electric
field at the midpoint O of the line AB joining the two charges?
(b) If a negative test
charge of magnitude 1.5 × 10–9 C is placed at this point, what is
the force experienced by the test charge?
Q.11. (a) Calculate
the potential at a point P due to a charge of 4 × 10–7C located 9 cm
away.
(b) Hence obtain
the work done in bringing a charge of 2 × 10–9 C from infinity to
the point P. Does the answer depend on the path along which the charge is
brought?
Q.12 Two charges 3 × 10–8 C
and –2 × 10–8 C are located 15 cm apart. At what point on the line
joining the two charges is the electric potential zero? Take the potential at
infinity to be zero.
Q13.
A slab of material of dielectric constant K has the same area as the
plates of a parallel-plate capacitor but has a thickness (3/4)d, where d
is the separation of the plates. How is the capacitance changed when the
slab is inserted between the plates?
Q.14 A parallel
plate capacitor with air between the plates has acapacitance of 8 pF .What will
be the capacitance if the distance between the plates is reduced by half, and
the space between them is filled with a substance of dielectric constant 6?
Q.15
Three capacitors of capacitances 2 pF, 3 pF and 4 pF are connected in parallel.
(a) What is the total
capacitance of the combination?
(b) Determine the charge
on each capacitor if the combination is connected to a 100 V supply.
Q.16 A 600pF capacitor is charged by a 200V supply. It is then
disconnected from the supply and is connected to another uncharged 600 pF
capacitor. How much electrostatic energy is lost in the process?
Q.17 Two tiny spheres carrying charges 1.5 µC and 2.5 µC are located
30 cm apart. Find the potential and electric field:
(a) at the mid-point of
the line joining the two charges, and
(b) at a point 10 cm from
this midpoint in a plane normal to the line and passing through the mid-point.
Q.18 The plates of a parallel plate capacitor have an area of 90 cm2
each
and are separated by 2.5
mm. The capacitor is charged by connecting
it to a 400 V supply.
(a) How much electrostatic
energy is stored by the capacitor?
(b) View this energy as
stored in the electrostatic field between the plates, and obtain the energy per
unit volume u. Hence arrive at a relation between u and the
magnitude of electric field E between the plates.
Q.19 A 4µF capacitor is charged by a 200 V supply. It is then
disconnected from the supply, and is connected to another uncharged 2 µF
capacitor. How much electrostatic energy of the first capacitor is lost in the
form of heat and electromagnetic radiation?
Q.20 A spherical capacitor has an inner sphere of radius 12 cm and
an outer sphere of radius 13 cm. The outer sphere is earthed and the inner
sphere is given a charge of 2.5µC. The space between the concentric spheres is
filled with a liquid of dielectric constant 32.
(a) Determine the
capacitance of the capacitor.
(b) What is the potential
of the inner sphere?
(c) Compare the
capacitance of this capacitor with that of an isolated sphere of radius 12 cm.
Explain why the latter is much smaller.
Q21 An electrical technician requires a capacitance of 2 µF in a
circuit across a potential difference of 1 kV. A large number of 1 µF
capacitors are available to him each of which can withstand a potential difference
of not more than 400 V. Suggest a possible arrangement that requires the
minimum number of capacitors.
Q.22 A condenser having capacity 2 F is charged to 200V
potential, its plates are joined to any resistance wires. What is the heat
produced?
Q.23 What is the net charge on a charged capacitor?
Q.24 What will happen to the capacity of a parallel
plate capacitor if area of each plate is doubled and distance between the
plates becomes halved?
Q.25 What happens to the electric field inside a
dielectric when it is placed in an external electric field?
Q.26What will be the effect on
potential if a medium of dielectric constant K is introduced?
Q.27 What would be the work done if a point charge
+q is taken from a point A to the point B on the circumference of the circle,
which is having a +q point charge at the centre?
Q.28 a) What is the unit of electric flux?
b) Is it correct that the capacitance of a spherical conductor is equal to the radius of the conductor in CGS system?
b) Is it correct that the capacitance of a spherical conductor is equal to the radius of the conductor in CGS system?
Q.29 Is electric potential
necessarily zero at a point where electric field strength is zero.
Q.30Does electric potential
increase along electric lines of forces.
Q.31 Four metallic plates each with surface area ‘A’ and
interplate separation ‘d’ are placed as shown. Alternate plates are connected
to points A and B. What is the equivalent capacitance of the system? 
Q.32 Four capacitors are connected as shown in the fig. What
is the equivalent capacitances between A and B?
Q.33 If a unit charge
is taken from one part to another part over an equipotential surface, then what
is the work done on the charge?
Q.34 Give the relation between the electric field and
potential for closely spaced equipotential surfaces.
Q.35 What are equipotential surfaces?
Q.36 What principle
do we use to find the potential at a point due to a system of charges?
Q.37 What is a Vande Graaff Generator? Draw a Vande Graaff
generator?
Q.38 What is electrostatic shielding? During thunderstorms
it is safer to be inside a car or stand under the tree.Explain your answer.
Q.39 In a parallel plate capacitor with air between the
plates has an area 6*10-3m2 and the distance between the
plates is 6 mm.find the capacitance of the capacitor.if this capacitor is
connected to a 200v supply, what is the charge on each plate of the capacitor?
Q.40The electric field at a point due to a point charge is
20Nc-1 and the electric potential at that point is 40jc-1
.Calculate the distance of the point from the charge and the magnitude of the
charge.
Q.41 A parallel plate condenser with plate area A is filled
with two dielectric K1 and K2 each occupying equal space
lengthwise. If the separation between two plates is t for each dielectric then
what is the capacity of the condenser.
Q.42 A parallel plate capacitor having a plate separation
2mm possesses a capacitance of 18PF.The capacitor is connected to a 100v
supply.Explain what would happen , if a 2 mm thick mica sheet of dielectric
const k=6 were inserted between the plates(a) while the voltage supply remains
connected.?(b) after the supply was disconnected.
Q.43 What is the potential energy of a dipole placed in an
external field? Also give an expression for Torque experienced by the dipole in
a uniform electric field. What will be the torque experienced by the dipole if
it is in the direction of the electric field?
Q.44 A 300PF capacitor is charged by a 200v supply.it is
then disconnected from the supply and is connected to another uncharged 300PF
capacitor.How much energy is lost in the process?
Q.45 Derive the
formula for effective capacitance when (i)Capacitors C1 and C2
are connected in series.
(ii)Capacitors C1 and C2 are connected in parallel.
What happen to the charge on the capacitor if it is disconnected from the battery?
(ii)Capacitors C1 and C2 are connected in parallel.
What happen to the charge on the capacitor if it is disconnected from the battery?
Q.46 Differentiate between electrostatic
potential and electrostatic potential energy?
A metal sphere 0.30 m in radius is positively charged with 2 C. Find the potential at distance 1m from the sphere and at the centre of the sphere.
A metal sphere 0.30 m in radius is positively charged with 2 C. Find the potential at distance 1m from the sphere and at the centre of the sphere.
Q.47 Two capacitors C
1 and C 2 are
charged to 120 V and 200 V respectively. It is found that by connecting
them together the
potential on each one can be made zero. Then :
(1) 3C1 = 5C2 (2)
3C1 + 5C2
= 0
(3) 9C1 = 4C2 (4) 5C1 = 3C2
Q.48 Define electric dipole moment. Write its S.I. unit
Q.49 . Write two limitations of
Coulomb’s law.
Q.50. What are the unit and
dimensions of permittivity of free space?
Q.51. Calculate the electrostatic
force between two α- particles at a distance of 2x10-5m between
them.
Q.52. Why do electric field lines
never cross each other?
Q.53. Derive an expression for
the electric field at a point on the equatorial line of an electric dipole.
Q.54. Does an electric dipole
always experience a torque, when placed in uniform electric field? Support your
answer with reason.
Q.55. How an electrostatic
potential is related to the electric field at a point?
Q.56. No work is done in moving a
test charge over an equipotential surface. Why?
Q.57. Derive an expression for
the potential energy of an electric dipole in an external uniform electric
field.
Q.58. What is meant by
‘electrostatic shielding’?
Q.59. Derive an expression for
the capacitance of a parallel plate capacitor? On what factors does the capacitance
of a parallel plate capacitor depend?
Q.60. Define dielectric constant
in terms of the capacitance of a capacitor.
Q.61. In a parallel plate
capacitor, how is the capacity affected, when without changing the
charge.
a. The distance between the plates
is doubled.
b. Area of the plates is halved.
Q.62. Derive an expression for
the energy stored in a parallel plate capacitor with air as the
core material of the capacitor.
Q.63 What does q1 + q2 Signify.
Physics By Er.shyam Pachori At C.L 81 D.D Nagar Gwalior
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