Rate of flow of electric charge through any point of the circuit is called electric current. = Unit – AMPERE
Current :- Flow of charge in conductor in called current.
Coulomb's law:-According to this law, the force of attraction or repulsion between stationary points charge is directly proportional to product of the charges and inversely proportional to square of distance between them.
Electric field It is the region surrounding an electric charge or group of charges, in which another charge experiences a force of attraction or repulsion.
Electric lines of forces:-An electric lines of force field along which a free isolated unit positive charge moves.
Properties (1) Electric lines of force start from positive charge and end to the negative charge. (2) No too line of force can intersect each other because if they do so, then at the point of intersection two tangents can be drain which would mean two directions of force at that point which is impossible. (3) These lines have a tendency to separate from each other in the direction perpendicular to their length. (4) Lines of force of uniform field are parallel. (5) Lines of force of leaves the surface of conductor normally
Electric Flux It is defined as that total number of lines of force passing normally through a curved surface placed in the field or the dot product of E and normal
OMH's law According to this law if there is no charge the physical state of conductor (Such as temp.) then the current flowing through the conductor in directly proportional to the vlg applied i, e.
I µV .
A graph between applied voltage and current in a straight line shows that it follows ohm's law Note:- Ohm's law is valid for metallic conductors only.
Resistance :- It is properly of
r = specific resistance or rextively.
Note:- The reciprocal of resistivity is called conductivity.
(Ohm – m)–1 = mho/meter..
Note:-(1) T - ,R- because heat causes atoms in the crystal tattice to vibrate more. (2) Resistance increase an a material become more disordered. (3) Best leanam conductor ® silver,, Tungsten ® light bulb fillament Nichrome ® Heater element in tooster..
COLOUR CODE FOR RESISTANCES
These resistances are usually carbon resistances and whose code is used to indicate the value of resistance. A carbon resistance has usually 4 concentric rings or bands A, B, C, D of different colours.
The colour of first two bands A and B indicate the Ist two significant figures of resistance in W & whose of 3rd band C indicate the decimal multiplies. The 4th band D (Which is either silver or gold) tells the tolerance. Sometime only 3 colours band A, B and C, B.
NOTE:- B. Roy Great Britain very good wife.
Electric Potential The electric potential at a point in an electric field in the ratio of the work done in bringing a test charge form infinity to that point to the magnitude of the test change. If the work done in moving a test charge q0 from infinity to that point against the field is W, then
Potential Gradient Rate of charge of potential w.r.t distance in called potential gradient.
Electric Potential Energy The electric potential energy of a system of charges is the work that has to be done in bringing these charges form infinity to near each other to form the system.
The potential energy of a system of charges q1 and q2 seperaled by a distance 'r' is
Capacitor An element in which energy is stored in the form of electrostatic field in capacitor.
Capacitance Defined as ratio of charge given to the plate of capacitor to the pot. diff produced between the
area of plate ® medium between plate D ® distance between plate
= 8.85 × 10–12
e 0 ® Permittivity of free space Unit – c2N–1 M–2 For a capacitor, V µq
Energy stered in capacitor
Inductor It is an element in which energy in stored in the form of electromagnetic field (Unit ® Henry.)
Energy stored in Inductor
Inductance Inductance result from the fact that a flow of current produces magnetic field, according magnetic field along tends to induce a vlg (or current) in a wire according to faradays's law
For RL Load V=Vm sin wt
show I lags by 90º R-L Load phaser :-
For RC Load
Shows I leads by 90º For RC phases
For RLC Load
Note:- Reactive power is consuned by energy storing demands