Electrostatics Flashcards
SI unit of charge
DIMENSION
Coulomb, scalar quantity
[AT]
1 m C
1 u C
1 n C
1 p C
10^-3 C
10^-6 C
10^-9 C
10^-12 C
Properties of Charge
- scalar quantity
- is transferrable
- is associated with mass
- charge is conserved
- charge is quantised
- addictive nature of electric charge
- like charges repel and unlike charges attracts
quantisation of charge
is the property by virtue of which all free charges are integral multiple of a basic fundamental unit of charge represented by electrons
Q = +_ ne
charge of electrons
1.6 X 10^-19 C
Additive nature of electric charge
the total electric charge on a body is equal to algebraic sum of all the charges located at different points
Ques: is a charge of 5.8X10^-18 C possible?
q = +_n e
5.6X10^-18 c = n * 1.6X10^-19c
36.25 : not possible
point charges
if the size of charged bodies are very small as compared to the distance b/w them, we treat them as point charges.
Coulomb’s Law
the electrostatic force of attraction or repulsion between two static point charges is directly proportional to the product of magnitude of 2 charges and inversely proportional to the square of distance between them
value of k depends on
- nature of medium separating the charges
- system of units
value of k in free space
k = 1/4piEo
9x10^9 Nm^2C^-2
[ ML^3 T^-4 A^-2]
Eo value in freespace
8.85 X10^-12 C^2N^-1m^-2
[M^-1 L^-3T^4A^2]
relative permeability
Er = Em/ Eo
Fo/Fm = Er
QUES: the electrostatic forces of 2 charges kept at certain distance in vacuum is F. If these are immersed in liquid, the force becomes F/4 provided separated becomes same. Find relative permeability of medium
using Fo/Fm = Er
F/
F/4 == 4
Absolute permittivity of free space
the degree upto which the electric charge influenced the air/vaccum