# what is displacement current????what is conduction current???

Conduction current is the electric current that flows through a conductor because of an applied potential difference.

Displacement current appears as a theoretical necessity in situations where non steady current is encountered. Suppose let us consider a charging capacitor (not has been completely charged yet) consisting of parallel plates as shown in the figure. Now it has been found that if we keep a magnetic needle between the plates it will shows a deflection indicating that there exists a magnetic field between plates.

Now according to Ampere circuital law there must exists a current flow to have a magnetic field according to the relation:

---1.

But between the plates there exists no conduction current, thus the contour C1 encloses no current thus.

---2.

Again, applying Ampere circuital law in contour C2 gives

---3.

But eqn. 1 and eqn. 2 gives a contradiction.

Thus to resolve the contradiction Maxwell proposed that Ampere circuital should be modified and an invisible current is to be considered that gives rise to a magnetic field between the capacitor plates. Thus, Ampere-Maxwell law became

---4.

Maxwell argued that the electric field is changed between the plates due to mounting charge on the plates and a changing electric field gives rise to a magnetic field.

Thus displacement current is the current that is included to explain the magnetic field inside the capacitor due to mounting up of charges on its plates.

Mathematically,

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In simple lang.   -   conduction current is the result of current due to charges at rest.displacement current is due to motion of charge carriers

The conduction current is

I=CdVdt

You know how V varies with respect to t. You will need to find C, which is not that difficult.

The displacement current D can be calculated from

Dt=ϵwdVdt
• -1

sry. for the blanks dr.    this reply doesn't support the formulas ....

• -16
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