ELECTROSTATICS Flashcards
what is electrostatics?
Electrostatics is the branch of physics that deals with the study of charges at rest.
What are point charges?
Two charges are said to be point charges if their sizes are smaller as compared to the distance between them
What is quantisation of charges?
Q = ne
Where n=1,2,3 …….
Minimum charge on an object can be
1.6 x 10^-19 C
1 C contains how many electrons
6.25 x 10^18 electrons
Columbs Law states that
There is a force of attraction or repulsion between two point charges. This force is directly proportional to the product of magnitude of point charges and inversely proportional to the square of distance between them.
Positive columb force is
Repulsive
Negative columb force is
Attractive
What is inverse square law
F ∝ 1/ r^2
K is called
Electrical constant
The value of k is
9 x 10^9 Nm^2/ C^2
Value for permittivity of free space is
8.85 x 10^-12 C^2/Nm^2
ε0 is
The permittivity of free space
ε is the
Permittivity of dielectric
εr is
Relative permittivity
Formula for Columbs Law is
On notes, derive it
Columbs Law for dielectric is
On notes, derive it
Columbs law for dielectric is ________ than Columbs law for free space
Greater
For every dielectric, εr is greater than
1
For polar materials, relative permittivity is
Infinite
Vectorial form of Columbs law
On notes, derive it
Write the three forms of force vectors
On notes, derive it
Columb force is maximum for _______ magnitude of charges and _________ distance between charges
Maximum, minimum
Columbs force is minimum for __________ magnitude of charges and __________ distance between charges
Minimum, maximum
When charges are touched/ combined, their magnitude is
Added
When charges are separated after combining, their magnitude is
Divided equally between the two
What is electric field?
The region or space around a charge in which it exerts force on the other charge.
What is electric intensity
The strength of electric field is called electric intensity. It is defined as force acting on a test charge.
The SI units of electric intensity are
Newton per columb
Volt per meter
The vector form of electric intensity
In notes
Electric field is _______ near the charge
Strong
Zero field of unlike charges is present
Outside near small charge
Zero field of like charges is present
Outside near the smaller charge
write the formulas for electric intensity
F/q not
k Q/ r square
formula for electric field for hollow charged sphere
zero
formula for electric intensity for charged plate
E = σ / 2ε0
σ is called
surface charge density
σ is equal to
Q/A
shortcut for finding electric intensity of oppositely charged plates if E for charged plate is given
multiply by 2
electric intensity for two oppositely charged plates is
E = σ / ε0
shortcut for finding electric intensity for a charged plate if E for oppositely charged plates is given
divide by 2
two charges Q1 and Q2 are exerting force on each other. F/Q2 is the electric intensity of
Q1
A charge of 5μC is placed at origin. Its electric intensity at 3i + 4j will be
1080i + 1440j
two charges 4μC and 16μC are placed at a distance of 3m. the zero field location from 4μC will be
SOLVE IT
1 m
two charges 3μC and -27μC are placed at a distance of 3m. the zero field location from 3μC will be
5 m
define electric field lines
the path followed by unit positive charge in an electric field is called electric field
the intensity of electric field depends on the __________ of electric field lines
proximity or closeness
define electric potential
it is defined as work done on unit positive charge against the electric field
formula for potential
V = W/q
unit for volt
joule per coulomb
base units for volt are
kg m2 s-3 A-1
△V
Fd/q
formula for potential gradient
E = -△V/△r
formula for potential difference if force isn’t given
V = kQ/r
what is zero potential point?
there is a point between two opposite charged where total potential is zero. it is called zero potential point.
