Concepts of electrical engineering

8/7/2019 Concepts of electrical engineering

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Concepts of electrical engineering

topic- dc networks and circuits

for making any electrical n/w and ckt we use some basic elements like resistor,

capacitor and inductor and some any other elements. if the excitation is dc then the n/w is called

dc n/w.

*what is the difference btwn n/w and ckt?

ans- n/w consists of active and passive elements may be posibility both are not use

together.

ckt consists of active and passive elements and have a closed loop which is compalsary.

*what is active and passive elements?

ans- active elements are those elements which gives energy to the n/w and ckt.ex-v/g and

current source.

passive elements are those elements which takes energy from active elements and store it

in another form of energy or dessipates energy.

ex-resistor,capacitor and inductor.


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note-

1.all electrical ckt are called electrical n/w but all electrical n/w are not called

electrical ckt.

2.resistor is known as energy dessipative element and energy sroring elements arecapacitor and inductor.capacitor stores energy in the form of electrostatic energy

and inductor stores energy in the form of electromagnetic energy.

resistor-it absorbs energy and dessipate it in the form of heat.

p=i*i*r

capacitor-absorbs energy and stores it in the form of electrostatic energy.

u=1/2*c*v*v

inductor-absorbs energy and stores it in the form of electromagnetic energy.

E=1/2*l*i*i

*what is current?

ans-it can be produced by the movement of electrical charge.or it is defined as the rate of

change of charge w.r.t. time.

i=dq/dt (ampere(s.i. unit))

note-

1.the current is always flow from higrer potential to lower potential.

*what is voltage?

ans-the voltage or potential diff. btwn two points is defined as the work to be done in

joules to move one coulomb charge from one pt. to another pt.

v=I *r (volt)


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*what is power?

ans-power of dc ckt is equal to the product of dc voltage and total current flow in the

ckt.or transfer of energy w.r.t. time.

p(dc)=v*i (watt)

*what is electrical energy?

ans-it is defind as the product of electrical power to the particular time.

e=p*t (watt-hour)

*what do u mean by open ckt?

ans-any electrical ckt is called to be an open ckt if there is no flow of current btwn anytwo pts. Of ckt. open ckt have very high resistance. the power in open electrical ckt is 0.

*what do u mean by short ckt?

ans-any electrical ckt is said to be a short ckt when the flow of current is very high.in

that case r=very small(not zero).

*what is linear elements?

ans-those elements which have linear v-i characterstics.and the n/w made by linear

element is called linear n/w. (ex-r,l,c)


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*what is non linear elements?

ans-those elements which have non linear v-i characterstics.and the n/w made by the

non linear element is called non linear n/w. (ex-diode,trasmitter,op-amp)

*what is bilateral elements?

ans-if the relation btwn v and i remains constt. or does not change by changing the

polarities of the ckt are called bilateral elements.(ex-r,l,c)

note- it does not depend upon the flow of current.

*what is unilateral elements?

ans-those elements by changing the position or polarity of terminal v and i chara.

changes elements called unilateral elements.(ex-diode)

note-it depends upon the flow of current.

*what is lumped n/w?

ans-in this n/w elements can seperated physically.


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*what is distributed n/w?

ans-in elements are not seperated physically.(transmission line)

topic-conceot of linearity

*we have alreadyknow that linearn/w is the n/w the chara. of which do not change

with change of v/g and current.

*if the n/w chara change with change in time,temp or any other parameter then it willbe called as non linear n/w.

*r,l,c as a linear elements-

a ckt element is called ideal if the v/g across it and current

through it are related by

*a constt. proportionality(resistor)

*a differential relationship(capacitor)

*a integral relationship(inductor)

these relationship can be shown to be linear so r,l,c are called

linear element.

* r as a linear element-

1-v=i*r

2-power dessipation p=i*i*r

3-the resistance of a resistor is depend upon the temp.

* c as a linear element-


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1-q=c*v

or i=c*dv/dt

or v=1/c(integration of i w.r.t. time)

2-energy stored in capacitor

E=1/2*c*v*v

3-a capacitor acts as a linear element if and only if charged or

discharged at a constt. rate becz only then its v/g and current chara. will be linear.

*l as a linear element-

1-v=l*di/dt

2-energy stored in inductor

E=1/2*l*i*i

3-as inductor needs to be unsaturated so that its operation

would take place on the linear region of the hysteresis curve of the inductor only then it will

behave linearity.

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Concepts of electrical engineering