CLASS 12 PHYSICS NOTE CHAPTER 1 ELECTRIC CHARGE AND FIELDS
Electric charge is the character of the body due to get it applied for some other body.
OR
The excess of Lake of an electron to an object is called electric charge.
S.I. Unit is Coulomb C.
Its other unit are mille Coulomb (mC), micro Coulomb, nano Coulomb (nC)
1 mC = 10^ -3 C
1 micro Coulomb = 10^-6 C
1 nC = 10^-9 C
Production of Charge
BY FRICTION
By rubbing two object both can be charged if we further connect then both become in electrically neutral .
This proves that charge are to type
Positive
Negative
Here number of positive and negative will be equal.
Like charge are repel but opposite charge are attract to each other.
BY INDUCTION
When a charge body is brought near uncharge body the charge in uncharge body get polarized this phenomenon is called electrostatic induction.
BASIC PROPERTIES OF ELECTRIC CHARGE
ADDITIVITY OF CHARGES
Is the property by virtue of which total charge of a system is obtained simply by adding algebric are the charge present anywhere on the system
It means charge are is scalar like mass of a body and added by simple of mathematics.
example = 1.If a system containing charge Q1 Q2 Q3 ......... Qn then the total charge of the system is q = q1 + q2 + q3 +......... +qn.
2. If a system contains charge +2q,-3q,+5q,-q.
Then the total charge
q = +2q-3q+5q-q
= +3q
CONSERVATION OF CHARGE
Total charge of an isolated system is always conserved .
Charge can be neither be created nor be destroyed it can only be transferred from one body to another body so that net charge is always zero .
QUANTISATION OF CHARGE
The quantization of charge is the property by virtue of which are free charges are integral multiple of basic unit of charge of of an electron or Proton are represent e.
COULOMB`s LAW
This law state that the force of attraction or repulsion between two stationary point charges directly proportional to the product of the magnitude of the two charged and inversly proportional to the square of the distance between them.
This force act long the line joining the two charge.
If two point charge Q1 and Q2 are separated by a distance R then force between them is given by
q1 r q2
F proportional | q1 q2 |
F proportional 1/ r^2
F proportional | q1 q2|/ r^2
F = K |q1 q2|/r^2
Where K = electrostatic force constant
The value of k depend on the nature of the medium between the two charge.
PERMITTIVITY
primitive is a property of the media which determine the electric force between two charges situated in the medium.
ELECTRIC FIELD
The region bond a given charge in which other charge experience and electric force is called an electric field .
the force between two charges separated by a distance R is given F = KQq/r^2
where Q is the source charge and q test charge.
ELECTRIC FIELD LINES
electric field lines due to positive charge radially outward .
the electric field lines due to negative charge radially inward .
the direction of electric field is positive to negative .
properties of electric field lines
electric field lines start from positive charge and end from negative charge .
electric field lines do not intersect Each Other because every intersect each other then at point of intersection we can what Tut agent which keep to direction of electric field at that point which is not possible .
electric field line do not form closed loop
in charge free region electric field line are continuous curve without any break .
ELECTRIC FIELD INTENSITY
the number of electric field line passing perpendicular to per unit area of a given surface is collective field intensity .
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