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, Electrostatics
(Electric Field & Potenial)
ELECTROSTATICS / FIELD
Electrostatics is a branch of physics which deals with charge at rest charge is the origin of electromagnetic
force. When charge is at rest then region around it called electric field while the region around the moving
charge called magnetic field.
PROPERTIES OF CHARGE :
1. For a given closed system the total charge remains conserved.
2. Charge is always quantised i.e. Q = ±nc ; n I
Charge on any body is always in the integral multiple of one electronic charge (e = 1.6 × 10–19 coul).
3. Charge is relativistically invariant.
TYPES MATERIAL
There are three kinds of material on the basis of conductivity.
(a) Conductor : Having large number of mobile electrons. It is approximately 1021 electrons/c.c.
(b) Bad conductor : Having very small number of free electrons, it is approximately 107 electrons c.c
(c) Semi conductor : Conductivity lies between conductor and insulator. Number of free electrons is
approximately 104 electron/c.c.
COULOMB’S LAW :
When two point charges q1 and q2 are separated by a distance r then force of mutual intraction F is given by
F q1q 2 when r = constant.
1
and F when q1q2 = constant
r2
q1q 2 qq
Hence F 2
or F k. 1 2 2 ; K is proportionality constant
r r
1 q1q 2 1 9
In SI units, F . 0 8.85 1012 Fm and 4 9 10 nt m coul
2 –2
4 0 r 2 ; 0
q1q 2
In cgs units, F ; 0 is per mittivity of the vacuum.
r2
When there is a medium in the intervining region of two charges then
1 qq
F . 1 2 2 ( Îr is the relative permitivity of medium)
4 0 r r
Îr is the relative permitivity which is the dimensionless qunatity that gives the factor by which force is
reduced compared to vaccum.
[1]
JEE Main JEE Adv. BITSAT WBJEE MHT CET and more...
4.8 50,000+ 2,00,000+
Rating on Google Play Students using daily Questions available
With MARKS app you can do all these things for free
Solve Chapter-wise PYQ of JEE Main, JEE Advanced, NEET, BITSAT, WBJEE, MHT CET & more
Create Unlimited Custom Tests for any exam
Attempt Top Questions for JEE Main which can boost your rank
Track your exam preparation with Preparation Trackers
Complete daily goals, rank up on the leaderboard & compete with other aspirants
4.8 50,000+ 2,00,000+
Rating on Google Play Students using daily Questions available
, Electrostatics
(Electric Field & Potenial)
ELECTROSTATICS / FIELD
Electrostatics is a branch of physics which deals with charge at rest charge is the origin of electromagnetic
force. When charge is at rest then region around it called electric field while the region around the moving
charge called magnetic field.
PROPERTIES OF CHARGE :
1. For a given closed system the total charge remains conserved.
2. Charge is always quantised i.e. Q = ±nc ; n I
Charge on any body is always in the integral multiple of one electronic charge (e = 1.6 × 10–19 coul).
3. Charge is relativistically invariant.
TYPES MATERIAL
There are three kinds of material on the basis of conductivity.
(a) Conductor : Having large number of mobile electrons. It is approximately 1021 electrons/c.c.
(b) Bad conductor : Having very small number of free electrons, it is approximately 107 electrons c.c
(c) Semi conductor : Conductivity lies between conductor and insulator. Number of free electrons is
approximately 104 electron/c.c.
COULOMB’S LAW :
When two point charges q1 and q2 are separated by a distance r then force of mutual intraction F is given by
F q1q 2 when r = constant.
1
and F when q1q2 = constant
r2
q1q 2 qq
Hence F 2
or F k. 1 2 2 ; K is proportionality constant
r r
1 q1q 2 1 9
In SI units, F . 0 8.85 1012 Fm and 4 9 10 nt m coul
2 –2
4 0 r 2 ; 0
q1q 2
In cgs units, F ; 0 is per mittivity of the vacuum.
r2
When there is a medium in the intervining region of two charges then
1 qq
F . 1 2 2 ( Îr is the relative permitivity of medium)
4 0 r r
Îr is the relative permitivity which is the dimensionless qunatity that gives the factor by which force is
reduced compared to vaccum.
[1]
