Electrostatics Notes by Sir Waqar Hussain
Important Easy Notes of Physics of Chapter No. 12: Electrostatics written by Professor Mr. Waqar Hussain Suib. These notes are very helpful in the preparation of Physics for students of the 12th class and these are according to the paper patterns of all Sindh Book Boards.
Summary and Contents:
Topics which are discussed in the notes are given below:
- State and Explain Coulomb’s Law with Mathematical Representation
- State and Explain Electric Field
- Definition of Test Charge
- Definition of Electric Field Intensity and Mathematical Representation
- Definition of Electric Lines of Force and Properties of Electric Lines of force
- Define and Explain Electric Flux and Mathematically
- Electric Flux due to a Point Charge in a Closed Sphere
- Define and Explain Gauss’s Law and Mathematically
- Application of Gauss’s Law
- The Electric Field Due to a Thin Spherical charged Shell
- Field intensity inside the Shell
- Field intensity on the surface of Shell
- Field intensity outside the Shell
- Electric Field Due to an infinite charged Sheet
- Electric Intensity Due to Two Oppositely Charged
Sheets
- Define and Explain Electric Potential with Mathematical Explanation
- Define and Explain Electric Potential Difference OR Potential Difference and Mathematical Explanation
- Relation between Electric Field and potential Difference
- Absolute Potential near an Isolated Point Charge
- State Electron-Volt
- Define and Construct Capacitor with Mathematical Explanation
- Define Parallel Plate capacitor and Expression for Capacitance
- Effect of Dielectric on Capacitance
- Capacitance of a Parallel Plate Capacitor When Dielectric is
Completely Filled between the Plates
- Combination of Capacitors:
Capacitors connected in parallel and Capacitors connected in Series.
- An oil drop having a mass of 0.002kg and charge equal to 6 electron’s charge is
suspended stationary in a uniform electric field. Find the intensity of electric field.
(Charge of electron = 1.6 x 10–19C)
- Calculate the potential difference between two plates when they are separated by a
distance of a 0.005m and are able to hold an electron motionless between them.
(Mass of electron = 9.1x10–31 Kg)
- Calculate the equivalent capacitance and charge on 5µF capacitor as show in the figure
- Two horizontal parallel metallic plates, separated by a distance of 0.5cm are connected
with a battery of 10 volts. Find:
1. The electric field intensity between the plates.
2. The force on a proton placed between the plates.
- Two capacitors of capacitance 400µF and 600µF are charged to the potential difference
of 300volts & 400volts respectively. They are then connected in parallel. What will be
the resultant potential difference and charge on each capacitor?
- A thin sheet of positive charge attracts a light charged sphere having a charge –5x10–6 C
with a force 1.69N. Calculate the surface charge density of the sheet.
(Єo = 8.85x 10–12 C
2
/Nm2
)
- A particle of mass 0.5g and charge 4 x 10–6C is held motionless between two oppositely
charged horizontal metal plates. If the distance between them is 5mm, find:
(i) The electric intensity (ii) The potential difference between the plates.
- A capacitor of 200 pF is charged to a P.D. of 100 volts. Its plates are then connected in
parallel to another capacitor and are found that the P.D. between the plates falls to 60
volts. What is the capacitance of the second capacitor?
- Calculate the force of repulsion on +2 x 10–8 coulomb charge. If it is placed before a
large vertical charged plate whose charge density is + 20 x 10–4 coulombs/m2
.
- Two capacitors of 2.0 µF and 8.0µF capacitance are connected in series and a potential
difference of 200 volts is applied. Find the charge and the potential difference for each
capacitor.
- A charged particle of –17.7 μC is close to a positively charged thin sheet having surface
charge density 2 x 10–8Coul/m2
. Find the magnitude and direction of force acting on the
charged particle.
- A parallel plate capacitor has the plates 10cm x 10cm separated by a distance of 2.5cm.
It is initially filled with air, what will be the increase in its capacitance if a dielectric slab
of the same area and thickness 2.5cm is placed between the two plates? (Take ЄR = 2)
- Find the equivalent capacitance in the given circuit and charge on each capacitor:
- A small sphere of weight 5 x 10–3N is suspended by a silk thread 50mm long which is
attached to a point on a large charge insulating plane. When a charge of 6 x 10–8C is
placed on the ball the thread makes an angle of 30° with the vertical; find the charge
density of the plane.
- A proton of mass 1.67 x 10–27 kg and a charge of 1.6 x 10–19C is to be held motionless
between two horizontal parallel plates 10cm apart: find the voltage required to be
applied between the plates.
- A particle carrying a charge of 10–5C starts from rest in a uniform electric field of
intensity 50Vm-1 Find the force on the particle and the kinetic energy it acquires when it
is moved 1m.
- An electron has a speed of 106 m/s. Find its energy in electron volts.
- How many electrons should be removed from each of the two similar spheres, each of
10 gm, so that electrostatic repulsion is balanced by the gravitational force?
- How many excess electrons must be placed on each of the two small spheres placed
3.0cm apart if the force of repulsion between the spheres is 10–19N?
- A capacitor of 12 F is charged to a potential difference 100V. Its plates are hen
disconnected from the source and are connected parallel to another capacitor. The
potential difference in this combination comes down to 60V. What is the capacitance of
the second capacitance?
- A proton of mass 1.67 x
27 10−
kg and charge 1.6 x
19 10−
C is to be held motionless
between two horizontal parallel plates 6cm apart; find the voltage required to be
applied between the plates.
- How many electrons should be removed from each of two similar spheres each of
10 gm so that electrostatic repulsion may be balanced by gravitational force.
- A proton of mass 1.67х10–27 kg and charge 1.6 х10–19C is to be held motionless between
two parallel horizontal plates. Find the distance between the plates when the potential
difference of 6 x 10–9 volts is applied across the plates.
- Two-point charges of +2 x 10- 4 C and -2 x 10- 4 C are placed at 40 cm from each other. A
charge of +5 x 10- 5 C is placed midway between them. What is the magnitude and
direction of force on it?
- The surface charge density on a vertical metal plate is 25x10-6 C/m2. find the force
experienced by a charge of 2 x 10-10C placed in front close to the sheet.
- A 10µF capacitor is charged to a potential difference of 220V. It is then disconnected
from the battery. Its plates are connected in parallel to another capacitor and it is found
that the potential difference falls to 100V. What is the capacitance of the second
capacitor?
- A thin sheet of positive charge attracts a light charged sphere having a charge –5x10–6 C
with a force 1.69N. Calculate the surface charge density of the sheet.
(Єo = 8.85x 10–12 C
2
/Nm2
)
- How many electrons should be removed from each of two similar spheres each of 10 gm
so that electrostatic repulsion may be balanced by gravitational force (Gravitational
constant = G = 6.67 x 10–11Nm2
/Kg2 and K = 9 × 10911Nm2
/C2
)?