8/4/2019 cse_qa

1/4

UNIT IELECTRIC CIRCUITS AND ELECTRON

DEVICES

1. Define current?The flow of free electrons in a metal is calledelectric current. The unit of current is theampere. Current (I) = Q/t, Where Q is totalcharge transferred & T is time required fortransfer of charge.

2. What is voltage?The potential difference between two points inan electric circuit called voltage. The unit ofvoltage is volt. It is represented by V or v.Voltage = W/Q = workdone/Charge

3. Define power.The rate of doing work of electrical energy orenergy supplied per unit time is called the

power. The power denoted by either P of p. It ismeasured in Watts. (W).Power = work done in electric circuit/TimeP = dw/dt = dw/dq.dq/dtP = VI

4. What is network?Interconnection of two or more simple circuitelements is called an electric network.

5. Distinguish between a branch and a nodeof a circuit.A part of the network which connects the various

points of the network with one another is calleda branch. A point at which two or more elementsare jointed together is called node.

6. Define active and passive elements.The sources of energy are called active element.Example: voltage source, current source.The element which stores or dissipates energyis called passive element. Example: Resistor,Inductor, Capacitor.

7. Define unilateral and bilateral elements.In unilateral element, voltage current relation is

not same for both the direction. Example: Diode,Transistors.In bilateral element, voltage current relation issame for both the direction. Example: Resistor

8. Define linear and non-linear elements.If the element obeys superposition principle,then it is said to be linear elements. Example:Resistor.

If the given network is not obeying superpositionprinciple then it is said to be non linearelements.Example: Transistor, Diode.

9. Define Lumped and distributed elements.Physically separable elements are calledLumped element. Example : Resistor, Capacitor,Inductor.A distributed element is one which is notseparable for electrical purpose.Example: Transmission line has distributorresistance, capacitance and inductance.

10. How are the electrical energy sourcesclassified?

The electrical energy sources are classified into:1. Ideal voltage source2. Ideal current source.

11. Define an ideal voltage source.The voltage generated by the source does notvary with any circuit quantity. It is only a functionof time. Such a source is called an ideal voltagesource

12. Define an ideal current source.The current generated by the source does notvary with any circuit quantity. It is only a function

of time. Such a source is called as an idealcurrent source.

13. What are independent source?Independent sources are those in which, voltageand current are independent and are notaffected by other part of the circuit.

14. What are dependent sources?Dependent sources are those in which sourcevoltage or current is not fixed, but is dependenton the voltage or current existing at some otherlocation in the circuit.

15. What are the different types of dependentor controlled sources?(i) Voltage Controlled Voltage Sources (VCVS)(ii). Current Controlled Voltage Sources (CCVS)(iii). Voltage Controlled Current Sources (VCCS)(iv). Current Controlled Current Sources (CCCS)

8/4/2019 cse_qa

2/4

16. What is resistance?It is the property of a substance which opposesthe flow of current through it. The resistance ofelement is denoted by the symbol R. It ismeasured in Ohms. R = PL / A

17. What is average value?It is defined as area under one complete cycle toperiod. The average value of the sine wave isthe total area under the half-cycle curve dividedby the distance of the curve.Average value = Area under one complete cycle

Period

18. Define R.M.S. value.The r.m.s value is determined by taking themean of the squares of the instantaneous valueof current over one complete cycle.RMS = (Area under hatched line)

2

Period

19. Define form factor.The ratio of RMS value to the average value iscalled the Form factor.Form factor (Kf) = RMS value

Average Value

20. Define peak factor.Peak factor is defined as the ratio of themaximum value to the rms value.Peak Factor (Kp) = Maximum value

RMS value

21. Define Ohms law.The current flowing through the electric circuit isdirectly proportional to the potentialdifferenceacross the circuit and inversely proportional tothe resistance of the circuit,provided thetemperature remains constant.

22. Define Kirchoffs current law.Kirchhoffs current law states that in a node, sumof entering current is equal sum of leavingcurrent. I at junction point = 0

23. Define Kirchoffs voltage law.Kirchhoffs Voltage Law (KVL) states that thealgebraic sum of the voltages around anyclosed path is zero.Around a closed path V = 0.

24. Two resistances with equal value of Rare connected in series and parallel. What isthe equivalent resistance?Resistance in series Req = R1+R2

Resistance in parallelR eq = R1R2 / R1+R2

25. Two inductors with equal value of L areconnected in series and parallel what is theequivalent inductance?Inductance in series L eq = L

1+ L

2

Inductance in parallel L eq =L1+L2 / L1L2

26. Two capacitors with equal value of Care connected in series and parallel. What isthe equivalent capacitance?Capacitance in series C eq = C1C2/ C1+C2Capacitance in parallel C eq = C1 + C2

27. Write down the formula for a starconnected network is converted into a deltanetwork?28. Write down the formula for a delta

connected network is converted into a starNetwork?

*** refer class notes***

29. Distinguish between a cycle, time periodsand frequency.One complete set of positive and negativeinstantaneous values of the voltage or current iscalled cycle.The time taken by an alternating quantity tocomplete one cycle is called time period (T).The number of cycle that a alternating quantitycompleted per second is known as

frequency. It is measured in HZ.

Frequency (f) = 1/T

30. What is instantaneous value?The value of an alternating current, at anyparticular moment is called its instantaneousvalue.

32. What is average value?The average value of the sine wave is the totalarea under the half-cycle curve divided by thedistance of the curve.

33. Define phase angle.The angle between voltage and current is calledphase angle. It is denoted by .

34. What is impedance?The ratio of the phasor voltage to the phasorcurrent is called impedance It is denoted as Zand it is measured in Ohm.

Impedance (Z) = V/I

8/4/2019 cse_qa

3/4

35. State superposition theorem.Any electric circuit (linear, lumped, bilateral), isenergeied by two or more sources, the responsein any element in the network is equal to thealgebraic sum of the responses caused byindividual sources acting separately.

36. State Thevenins Theorem.A complex network having linear, bilateral,lumped elements with open circuited outputterminals can be reduced by a simple circuitconsisting of a single voltage source in serieswith a resistance (impedance).

***Draw the equivalent circuit***

37. State Nortons theorem.Any electrical network (linear, lumped, bilateral)

with short circuited terminals can be reduced bya simple circuit consisting of a single currentsource in parallel with a Thevenins equivalentresistance.

38. State Maximum power transfer theorem.Power transferred from source to load will bemaximum, when source resistance is equal toload resistance looking back from its loadterminals.

39. Define duality.Two electrical network which are governed bythe same type of equations are called duality.

40. Derive the expression for Maximum Powertransferred to the load.

PART B1. Try solving different networks using mesh

(loop) analysis and nodal analysis.

2. Solve networks using circuit theorems

Thevenins, Nortons and Superposition theorem.

***Refer class notes for worked

problems***3. State maximum power transfer theorem.

Derive an expression for maximum power

delivered.

4. State and prove maximum power transfer

theorem for ac circuits.

***Refer class notes ***

UNIT IITRANSIENT RESONANCE IN RLC CIRCUITS

1. What is transient response?The storage elements deliver their energy to theresistances, hence the response changes withtime, gets saturated after sometime, and isreferred to the transient response

2. Define time constant or RL Circuit.The time taken to reach 63.2% of final value in aRL Circuit is called the time constant of RLcircuit.Time constant (t) = L / R

3. Define time constant of RC Circuit.The time taken to reach 36.8% of initial currentin an RC circuit is called the time constant of RCcircuit.

Time constant (t) = RC.

4. What is meant by natural frequency?If the damping is made zero then the responseoscillates with natural frequency without anyopposition, such a frequency is called naturalfrequency of oscillations, denoted as

5. Define pole and zero.The network function N (S) will become infinite.Hence the roots of denominator polynomial P1,P2, P3,Pm are called poles of networkfunction.The network function N(S) will become zero.

Hence the roots of numerator polynomial Z1, Z2,Z3..Zn. are called zeros of networkfunction.

6. When the circuit is said to be inresonance?

i) A network is in resonance when thevoltage and current at the network inputterminals are in phase.

ii) If inductive reactance of a networkequals capacitive reactance then the network issaid to be resonance

7.What is resonant frequency ?The frequency at which resonance occurs iscalled resonance frequency. f = 1/2LC

8. Define bandwidth.The bandwidth (BW) is defined as the frequencydifference between upper cut-off frequency (f2)and lower cut-off frequency (f1)Bandwidth = f2-f1

8/4/2019 cse_qa

4/4

Where f2= upper cut-off frequency, f1= lowercut-off frequency

9. Define selectivity.Selectivity is defined as the ratio of bandwidth tothe resonant frequency of resonant circuit.

Selectivity = BW/resonant frequency = BW/fr

10. Define quality factor.The quality factor is defined as the ratio ofmaximum energy stored to the energydissipated per cycle.Quality factor (Q) = Maximum energy stored percycle / Energy dissipated per cycle

11. Define half power frequencies ?The frequencies at which the power is half themaximum power are called half powerfrequencies.

12. Write down the formula for inductivereactance and capacitive reactance?

*** refer class notes***

13. Give the expression for quality factor ofseries RLC Circuit.Quality factor is Q = 1 / R L /C

14. Give the expression for quality factor ofparallel RLC Circuit.Quality factor is Q = R C / L

15. What are coupled circuits?If the transfer of energy occurs from one circuitto another circuit through mutualinduction, then the two circuits are said to becoupled.

16. What is meant by single tuned coupledcircuits.The coupled circuit is said to be single tunedwhen the secondary coil contains anadjustable capacitor which can be tuned toresonance.

17. What is meant by double tuned coupledcircuits.?A double tuned coupled circuits is a one in whichthe capacitor is present in bothprimary and secondary.

18. Give the applications of tuned circuits.1.Used in radio receivers.2.In amplifier circuits3.In communication circuits.

19. Give two difference between single anddouble tuned circuits?

i) A capacitor is introduced eitherprimary or secondary side for single tunedcircuits, but indouble tuned circuits , two capacitors , one inprimary and another in secondary areintroduced.

ii) Single tuned circuits are used toselect lower frequencies . but double tunedcircuits, areused to select particular band of frequencies .

PART-B1. Define resonance. Derive an expression for

resonant frequency in series RLC circuits.

2. Derive an expression for resonant frequency

in parallel RLC circuits.***Refer class notes ***

3. Solve problems in RLC circuits

***Refer class notes for worked problems***

____________________