arjun karnati

 Profile Answers by arjun karnati 

• Jan 19th, 2009

 

Good question. to answer this question first of all we need to study the terms resistance, inductance, capacitance on atom level. Generally what we know is

Resistance: which opposes the flow of electrons.
Inductance: which opposes rate of change of current.
Capacitance: which stores electricity.

if we go to atom level, in atom there are electrons and protons. atom is having valence bond next forbidden gap next conduction bond. if we want to make electron jump from valence bond to conduction bond in spite of forbidden gap, we need to apply some external energy to the atom. so that electron can jump from val bond to con bond and we can have current. here while jumping from val bond to con bond we need to overcome forbidden gap. So this is Resistance. resistance is same whether you apply the energy either dc or ac.

to under stand inductance first of all we need to know one more concept of atom.
we have applied energy to atom and electron is released to conduction bond. but still the proton is always trying to attract the electron to its valance band. here we are applying sinusoidal wave energy means for every half cycle energy or voltage or electron moving force is becoming zero. exactly at this zero voltage state the proton tries to attract the its loosing electron. our sinusoidal voltage continuously becomes zero for every half cycle. so always the protons continuously try to attract the electrons means protons are trying to oppose the flow of electrons which is caused due to our applied voltage.

with this concept u might have understood what is inductance.
inductance is directly proportional to frequency of applied voltage
frequency increasing means zero voltage stage is coming into picture very fast. zero voltage stage means protons attracting the electrons to restrict flow of electrons to conduction band.

Harish P. Girhe

 Profile Answers by Harish P. Girhe Questions by Harish P. Girhe

• Jan 16th, 2011

 

It is because of loads reactance. Reactance either capacitive or inductive that depends on frequency. XL=2(pi)FL Where f is supply frequency. In DC supply f=0 hence XL=zero. Similarly Xc=1/2(pi)F.C=0 in dc supply. Thats why only resistance is to be present in DC system.