Skip to main content

Electric flux density(D)

The force acting on a charge moving in an electromagnetic field, as given by the Lorentz force is associated two field vectors electric flux density(D) and the magnetic field intensity(H).


Electric flux density(D):



  • Electric flux is the normal (Perpendicular)  flux per unit area.

  • If a flux of \Phi passes through an area of A m^2 normal to the area then the flux density ( Denoted by D) is:D = \dfrac{\Phi}{A}

  • If a electric charge is place in the center of a sphere then the electric flux on the surface of the sphere is:


D = \dfrac{\Phi}{A} = \dfrac{Q}{4 \pi r^2} , where r =radius of the sphere.


The SI unit of electric flux is Coulomb per meter square.


Relation between Electric flux density and electric field intensity:


If we compare the formula for the


Electric flux Density given above with the formula for the Electric Field intensity ,  We see that:
D = \dfrac{Q}{4 \pi r^2}  and  E = \dfrac{Q}{4 \pi \epsilon_0 \epsilon_r r^2}


Where , \epsilon_0 = Permittivity of vacuum and  \epsilon_r = relative Permittivity.


Thus, We can conclude that:
D = \epsilon _0 . \epsilon _r . E      And,      E = \dfrac{D}{\epsilon_0 . \epsilon_r}

Labels:

Comments

Post a Comment

Popular posts from this blog

Lorentz force equation

  Lorentz Force Equation   The force experienced by current element in magnetic field is given as sum of force due to electric field and magnetic field.   Force due to electric field: A region is said to be characterized by an electric field if a particle of charge q moving with a velocity v experiences a force Fe, independent of v. The force, Fe, is given by              F e = qE ---------------------------------------- (1.1)                    E is the electric field intensity. Measured in newtons per coulomb (N/C) or volts per meter. Where volt is a newton-meter per coulomb. The line integral of E between two points A and B in an electric field region gives voltage between A and B. It is the work per unit charge done by the field in the movement of the charge from A to B. Force due to magnetic field: If a charged particle experiences a force which depends on v, then the region is said to be characterized by a magnetic field. The force, Fm, is given by                     F m =...
2 comments
Read more

P-N junction diode

A P-N junction diode is a basic diode. It is the combination of P-type and N-type semiconductor. symbol : P-N junction and potential barrier : A P-N junction is the basic building block of many semiconductor devices like diodes and transistors. P -n  junctions are formed by joining  n -type and  p -type semiconductor materials. Since the  n -type region has a high electron concentration and the  p -type a high hole concentration this difference in concentration creates density mismatch across junction which results to creation of potential barrier. The value of potential barrier v b  is 0.3 for germanium and 0.7 for silicon. Working : Forward bias: Application of positive charge at p-side pushes holes towards potential barrier and similarly negative charge at N-side pushes electrons towards barrier if input voltage is grater than potential barrier then electrons diffuse from the  n -type side to the p-type side. Similarly, holes flow by diffusion from the p-type side to the n-type side...
4 comments
Read more

photodiode

Introduction : A photo diode is a semi-conductor device, with a p-n junction and an intrinsic layer between p and n layers. It can be used as a light detector, which involves the conversion of light into current or voltage depending on mode of operation. [gallery ids="867,866" type="rectangular"] construction :   Working : When a photon of sufficient energy strikes the diode, it creates an electron-hole pair. This mechanism is also known as the inner photoelectric effect. If it occurs at the junction these carriers are swept from the junction by the built-in electric field of the depletion region. Thus holes move toward the anode, and electrons toward the cathode, and a photo current is produced. The total current through the photo diode is the sum of the dark current (current that is generated in the absence of light) and the photo current, so the dark current must be minimized to maximize the sensitivity of the device. Mainly it is operated in two modes 1.  Photo ...
1 comment
Read more