1
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Explain the
term : Static – electricity
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Static
electricity
- When two charges bodies are separated by insulating
medium, the charges remain stationary on the body.
- This is called static electricity.
- The branch of engineering which deals with the study
of static – electricity is called Electro statics.
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2
|
What do you mean by the molecule and atoms?
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Molecule
- The smallest part of the substance is called
molecule.
Atoms
- A molecule consists of one or more substance is
called as atoms.
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3
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When atom becomes positive ion and negative ion?
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Positive
ion and Negative ion
- If an atom loses an electron, it becomes positive
charged.
- This atom is known as positive ion.
- Similarly when atom gain an electron, it becomes
negative charged.
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4
|
Describe the main reason for production of electro
static charge when glass is rubbed with silk.
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Electro – static charges
- When glass is rubbed with silk, glass loses
electrons to silk and therefore it becomes positive charged.
- Similarly when Ebonite is rubbed with fur, Ebonite
gains electrons from fur and becomes negative charged.
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5
|
Describe the importance of permittivity.
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Importance
of permittivity
- The permittivity affects the magnitude of the force
between two point charges.
- Higher the value of permittivity placed between two
point charges lesser the force between them and vice versa.
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6
|
State the value of the absolute Permittivity for
air.
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Absolute Permittivity
- The absolute permittivity of the air ( ε0 )
or vaccum is minimum and its value is limited to 8.854 × 10-12
farad / meter.
- The value of absolute permittivity of other material
is more than ε0.
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7
|
Define: Relative Permittivity
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Relative
permittivity ( εr )
- The ratio of the absolute permittivity of the some
material to the absolute permittivity of the air is called as relative
permittivity. Therefore
εr
= ε / ε0
Where
εr = Relative permittivity of the material
ε = Absolute
permittivity of the material
ε0 = Absolute permittivity of the air ( Farad / Meter )
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8
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State the Coulomb’s first and second law.
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Coulomb first law
- The first law explains the nature of the force between
two charged bodies.
- It states that’ like charges of electricity repel
each other whereas unlike charges attract each other’.
Coulomb second law
- The second law explains the magnitude of the force
between two charges.
- It states that ‘ The force between two charges is
directly proportional to the magnitude of the charges and inversely
proportional to the square of the distance between two charges.’ Therefore
F α ( Q1 × Q2 ) / d2
F
= k ( Q1 × Q2 / d2 )
Q1 =
Magnitude of the charge 1
Q2 = Magnitude of the charge 2
d2 =
Distance between two charge
k = Constant
= 1 / 4πε0εr
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9
|
Define : Electric field
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Electric
field
- The limited space region around charged body in
which an electric charge experiences a force of attraction or repulsion is
called an electric field.
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10
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Define : Electric lines of force or flux
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Flux ( Electric
line of force )
- The electric imaginary field lines around charged body
is called as electric lines of flux.
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11
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Why electric lines of force do not intersect?
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Electric Lines of Force
- The direction of the electric lines of force is from
positive charged body to the negative charged body.
- The electric lines of force do not intersect because
at the point of the intersection there are two directions of the field and it
is not possible.
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12
|
Why current does not flow in the dielectric
material?
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Dielectric Material
- When the potential difference is applied across an
insulating material, current does not flow because valance electrons are
tightly bound to its nucleus and no free electrons are available for
conduction of current.
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13
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Define : Electric flux, Electric flux intensity and Electric
Potential
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Electric flux
- The electric field is represented by electric flux
lines.
- The numbers of lines of force eliminating from
positive charged particle ( or body ) is called as electric flux. Its unit is
coulomb.
Electric flux intensity
- It is defined as electric flux passing through unit
area at the right angle to the direction of the field. Its unit is
coulomb/meter2
OR
- It is defined as force experienced by a unit
positive charge placed at that point.
Electric potential
- The electrical potential at any point is equal to
the work done required to bring a unit positive charge from infinity to that
point against the electric field.
- Its unit is Joule / coulomb.
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14
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Define : Electric potential gradient, Electric field
intensity and Dielectric Strength
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Electric potential gradient
- It is defined as the rate of change of potential
with distance.
- Its unit is volt / meter.
Electric field intensity
- It is defined as force experienced by the unit
positive charge placed at that point.
- Its unit is Newton / coulomb.
Dielectric strength
- It is ability of the dielectric material to
withstand against breakdown.
- The dielectric strength is defined as the maximum
potential difference which can withstand by the dielectric material without
breakdown of it.
- It is expressed in kV / mm.
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15
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Explain the term : Induction
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Induction
- It is phenomenon in which
the uncharged body gets charged by proximity charged body.
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16
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State the potential of the earth.
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The potential of the earth
is zero.
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17
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Define : Potential
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Potential
- It is defined as the work
done per unit charge.
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18
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Define : Factor of safety for dielectric
|
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Factor of safety
- It is defined as the ratio
of dielectric strength of insulator to the electric field strength in the
dielectric.
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