GNANAMANI COLLEGE OF ENGINEERING

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

BASIC ELECTRICAL AND ELCTRONICS ENGINEERING

QUESTION BANK

Prepared by

GANDHI. R. M.E.

Lecturer/EEE

UNIT – I

ELECTRIC CIRCUITS AND MEASUREMENTS

PART – A (2 MARKS)

1. Define charge.

The total deficiency or addition of excess electrons in an atom is called its

charge.

Unit of charge: Coulomb

Constant charge is denoted by letter Q and charge varying with time is denoted by q

or q (t).

2. Define current.

Movement of electrons is called current. It is also defined as flow of charges.

Current I=

Movement of electrons always flow from negative to positive.

Unit of current is Ampere.

DC current: The current does not vary with time is called direct current. It is

denoted

by I.

AC current: The current varies with time is called alternating current. It is denoted

by i (or)i(t).

3. Define potential difference.

It is also called as voltage (or) electric potential.

It is defined as the energy required to move the unit of charge from one point to

other.

It is also defined as the difference of electric potential between the two points of the

conductor.

Electric potential=

Unit of voltage is volt (or)

It is denoted by letter V.

4. Define Power.

The rate of doing work is called power.

Power P=VI

P=

Unit of power is Watts (or) .It is denoted by letter P.

5. Define Energy.

The rate of doing work with time is called power. It is also called as the

capacity to do the work.

Unit of Energy is Watt-hour (or) .It is denoted by letter E (or) W.

6. Define Independent source.

It is defined as the source voltage independent of current flowing through it

and source current independent of voltage across it. It is indicated by circle with

polarity of voltage and direction of current. It is also called as uncontrolled sources.

Types of independent of sources.

(i)Voltage source

(ii)Current source

7. Define Dependent sources.

It is defined as the voltage source or current source depends on voltage or

current elsewhere in the given circuit. It is indicated by diamond shape. It is also

called as controlled sources.

Types of Dependent of sources.

(i)Voltage controlled voltage source (VCVS).

(ii) Voltage controlled current source (VCCS).

(iii) Current controlled current source (CCCS).

(iv) Current controlled voltage source (CCVS).

8. Define ideal voltage source.

The energy source which gives constant voltage across its terminals irrespective of

the current flowing through its terminal is called ideal voltage source. At any time the

value of voltage at load terminals remains same.

9. Define practical voltage source.

Practical voltage source gas small amount of resistance (Rse) in series with voltage

source.

Due to Rse, the voltage across load terminals decreases slightly with increase in

current.

10. Define time invariant voltage source.

The source in which voltage or current is not varying with time is called time

invariant sources. It is also called as DC sources. It is denoted by capital letters.

11. Define time variant voltage source.

The source in which voltage or current is varying with time is called time

variant sources. It is also called as AC sources. It is denoted by small letters.

12. Define resistance.

The property of opposition of flow of current is called resistance.

Unit of resistance: ohm

It is denoted by letter R.

Power dissipated in resistor P=I2R

13. Define inductance.

The property of opposition of flow of change in current is called inductance.

Unit of resistance: Henry

It is denoted by letter L.

Energy stored in the inductor E=

It stores the energy in the form of magnetic field.

14. Define capacitance.

The property of opposition of flow of change in voltage is called capacitance.

Unit of resistance: Farad

It is denoted by letter C.

Energy stored in the inductor E=

It stores the energy in the form of electrostatic field.

15. Define branch and node.

Branch: It is a portion of a circuit with two terminal connected to it. A

branch may contain one or more elements.

Node: It is a junction of two or more branches.

16. Define mesh or loop.

It is defined as a set of branches forming a closed path in a network.

17. Define active and passive elements.

Active element: Active elements are the elements which supply power or

energy to the network.

Ex. Voltage source, current source

Passive element: Passive elements are the elements which either store energy

or dissipate energy in the form of heat.

Ex. Capacitor and inductor=store the energy

Resistor=dissipate the energy

18. Define lumped and distributed network.

Lumped network: A network consisting of physically separable elements

such as resistor, capacitor and inductor is known as lumped network.

Ex.RLC network

Distributed network: A network consisting of elements that are not

separable for analytical purpose is known as distributed network.

Ex. Transmission lines(R, L ad C is distributed along its length)

19. Define bilateral and unilateral network.

Bilateral network: The voltage-currant relationship is same for current

flowing in either direction is called bilateral network.

Ex. R, L and C

Unilateral network: The network has different relationships between voltage

and current for the two possible directions of current.

Ex: Diodes, vaccum tubes

20. Define linear and non-linear network.

Linear network: The relationship between voltage and current is linear, then

the network is called linear network.

Ex:Resistance

Non-Linear network: The network which do not satisfy the linear voltage-

current relationship is called non-linear network.

Ex: Diodes, Zener Diodes

21. State Ohm’s law.

At constant temperature. the current flowing through the resistor is directly

proportional to voltage across the resistor.

, V=IR

Power dissipated in resistor P=

22. Write the limitations of ohm’s law.

(i)It is not applicable to non-linear devices such as diodes, zener diodes and

voltage regulators.

(ii)It is not applicable for non metallic conductors. Ex. silicon carbide

(iii)It is not applicable for arc lamps, electronic valves and electrolytes.

23. State Kirchoff’s current law.

It is also called as point law (or) Kirchoff’s first law.

It is defined as algebraic sum of currents meeting at any node is equal to zero.

(Or)

At any node, sum of incoming current is equal to sum of outgoing current

Sign convention:

Positive: current flowing towards junction.

Negative: current flowing away from junction.

24. State Kirchoff’s voltage law.

It is also called as mesh law (or) loop law (or) Kirchoff’s second law.

It is defined as algebraic sum of voltages around any closed path is equal to

zero.

(Or)

At any closed path, sum of voltage rise is equal to sum of voltage drop

Sign convention:

Voltage rise: current flowing from –ve to +ve terminal of battery. It must be

taken as positive.

Voltage drop: current flowing from +ve to -ve terminal of battery. It must be

taken as negative.

25. Write the characteristics of series connection of resistances.

(i)Same current flows through each resistance.

(ii)Supply voltage V is the sum of individual voltage drops across each

resistance.

(iii)Equivalent resistance is equal to sum of individual resistance.

(iv)Equivalent resistance is the largest of all individual resistance.

Ex. Decoration lamps.

26. Write the drawbacks of series connection of resistances.

(i)Any break in the one part of the circuit will break the current flow through

the rest of the circuit.

(ii)Current ratings of all electrical appliances are not same. So they are not

connected in series.

(iii)Voltages are additive. So it is not suitable for practical lighting loads.

27. Write the characteristics of parallel connection of resistances.

(i)Same voltage appears across each resistance.

(ii)Total current I is the sum of currents through each resistance.

(iii)Reciprocal of equivalent resistance is equal to sum of reciprocal of

individual resistance.

(iv)Equivalent resistance is the largest of all individual resistance.

Ex. Residential wiring.

ADDITIONAL UNIV QUESTIONS 2 MARKS

1. State Ohm’s law and its limitations.

2. State Kirchhoff’s law.

3. Derive the equation for equivalent resistance of number of resistors connected in

parallel.

4. What is meant by electric energy?

5. Distinguish between power and energy.

6. What are lumped circuits?

7. What is meant by electric power? Give different forms of expression for electric

power.

8. Draw power triangle.

9. Define time period and frequency of an alternating quantity.

10. Explain the terms (a) instantaneous value and (b) average value for an ac signal.

11. Draw sinusoidal, saw tooth and half- rectified sinusoidal waveforms.

12. Define form factor and peak factor.

13. Define power factor.

14. Give the advantages of phase system.

15. Distinguish between apparent power and true power.

16. Mention the 2 types of wattmeter.

17. Name the coils in the wattmeter.

18. What are the advantages and disadvantages of MI instruments?

PART – B

1. (i) State and explain Kirchoff’s law. (8)

(ii)Explain the working of a Dynamometer wattmeter with a diagram(8)

2. Define (i) RMS Value (16)

(ii)Average Value

(iii)Instantaneous Value

(iv)Real power

(v)Apparent power

(vi)Reactive power

(vii)Frequency

(viii)Balanced three phase circuit

3. Name the instrument used for measuring the electrical power consumed during a

specific period. Discuss its principle of operation with suitable diagram. (16)

4. (i)A series circuit has R=10Ω, L=50mH, and C=100μF and is supplied with 200V,

50Hz. Find (i) Impedance (ii) current (iii) power (iv) power factor (v) voltage drop

across the each element. (8)

5. (ii)Derive the equation for equivalent resistance of number of resistors connected

in parallel. (8)

6. Illustrate with a neat diagram, the construction and operation of a permanent

magnet moving coil. How could it be modified for use as (i) ammeter (ii) voltmeter

(16)

7. 400V is applied to three star connected identical impedances each consisting of a

40 Ω resistance in series with 3 Ω inductance reactance. Find (i) line current (ii) Total

power supplied (16)

8. Find the current through each branch by network reduction technique. (16)

9. Calculate a) the equivalent resistances across the terminals of the supply, b) total

current supplied by the source and c) power delivered to 16 ohm resistor in the circuit

shown in figure. (16)

10. In the circuit shown, determine the current through the 2 ohm resistor and the

total current delivered by the battery. Use Kirchhoff’s laws. (16)

11. (i) In the network shown below, find the current delivered by the battery. (10)

(ii) Discuss about voltage and current division principles. (6)

12.Find the current through branch a-b using mesh analysis shown in figure below.

(8)

13.Find the nodal voltages in the circuit of figure. (16)

14.Using Mesh analysis, find current through 4 ohm resistor. (16)

UNIT – II

ELECTRICAL MACHINES

PART – A (2 MARKS)

1. In what respect does a 1-phase Induction motor differ from a 3-phase Induction

motor?

Construction wise a plain 1-phase Induction motor is more or less similar to a

3-phase squirrel-cage Induction motor except that its stator is provided with

only 1-phase winding.

2. What are the inherent characteristics of plain 1-phase Induction motor ?

A plain 1-phase Induction motor is not used in practice due to the following

inherent characteristics

· A plain 1-phase Induction motor does not have any starting torque

· However, if the rotor is initially given a starting torque, by some means,

the motor can pick up its speed in a direction at which the initial torque is

given and deliver the required output.

3. Name the two different theories with which principle of 1-phase induction motors

are explained.

The two different theories are

· Double revolving field theory

· Cross field theory

4. State double revolving field theory.

Double revolving theory, formulated by Ferrari, states that a single pulsating

synchronous speed proportional to the frequency of the pulsating field.

5. Name any four types of 1-phase induction motors.

Based on the method of starting arrangement provided, the 1-phase Induction

motors are classified as follows

(i) Split-phase motor

(ii) Capacitor start motor

(iii) Capacitor start and run motor

(iv) Shaded pole motor

(v) Repulsion start Induction run motor

6. Why are centrifugal switches provided on many 1-phase Induction motors?

Centrifugal switches are provided on many 1-phase Induction motors to

disconnect the starting / auxiliary winding from the supply when the motor

reaches about 70% of its synchronous speed.

7. How is the direction of a capacitor start Induction motor be reversed?

The direction of rotation can be reversed by interchanging the terminals of

either the main winding or the starting winding.

8. State the principle of 3 phase IM?

While starting, rotor conductors are stationary and they cut the revolving

magnetic field and so an emf is induced in them by electromagnetic induction. This

induced emf produces a current if the circuit is closed. This current opposes the cause

by Lenz’s law and hence the rotor starts revolving in the same direction as that of the

magnetic field.

9. Induction motor can run at synchronous speed ? True or false? Explain .

No, if the speed of induction motor is Ns then the relative speed between the

rotating flux and the rotor will be zero and so no torque is produced.

10. An induction motor is generally analogous to ?

It is analogous to a winding rotating transformer with its secondary circuit

closed.

11. Can the starting torque of of a slip ring induction motor being increased?

Yes. It can be increased by adding resistances to the rotor.

12. What would happen if a 3 phase induction motor is switched on with one phase

Disconnected?

The motor is likely to burn .

13. What happens if the air gap flux density in an induction motor increases?

The increase in air gap flux increases iron loss and hence efficiency decreases.

14. State the advantages of skewing?

It reduces humming and hence quite running of motor is achieved.

It reduces magnetic locking of the stator and rotor.

15. State the condition at which the starting torque developed in a slip-ring induction

motor is maximum.

When R2=X2

16 What are the effects of increasing rotor resistance on starting current

and starting torque?

The additional external resistance reduces the rotor current and hence

the current drawn from the supply.

It improves the starting torque developed by improving the power factor in high

proportion to the decrease in rotor current.

17. What is slip of an induction motor?

The slip speed expressed as the ratio of synchronous speed is defined as slip.

Percentage slip S=Ns-N/Ns*100

18. How the magnitude of rotor emf is related to the slip in an I M?

Rotor circuit emf per phase E2r=SE2

19. How the frequency of rotor emf is related to the slip in an I M?

Frequency of rotor emf/current fr=Sfs

20. What is the normal value of slip of an I M operating at full load?

3 - 5%

21. Why is not possible for the rotor speed of an I M to be equal to the speed of its

rotating magnetic field?

The machine will not be able to develop any mechanical torque to run as a

motor.

22. State the condition at which the torque developed in a 3 phase induction motor is

maximum.

When R2=SX2

23. What are the advantages of slip-ring I M over cage I M?

(i) Rotor circuit is accessible for external connection.

(ii) By adding external resistance to the rotor circuit the starting current is

reduced with the added advantage of improving starting torque.

(iii) Additional speed control methods can be employed with the

accessibility in the rotor circuit.

24. What are the losses occurring in an I M and on what factors do they depend?

Magnetic losses Wi

Electrical losses Wcu

Mechanical losses Wm

For I M operating in normal condition (with constant voltage and frequency)

magnetic and mechanical losses remain constant whereas electrical losses

vary in square proportion to the current.

25. What care should be taken at the time of construction to reduce eddy current

losses in I M?

Make the resistance of the core body as large as possible.This is

achieved by laminating the stator core,stacked and revetted at right angles to

the path of eddy current.The laminations are insulated from each other by thin

coat of varnish.

26. Why is there not appreciable magnetic losses in the rotor core of Induction

motors?

Although the rotor core is also subjected to magnetic flux reversals and since

the frequency of flux reversals in the rotor, fr = Sfs, is very small, the iron loss

incurred in the rotor core is negligibly small.

27.How does the shaft torque differ from the torque developed in 3-phase Induction

motor?

The mechanical power developed Pd causes the rotor to rotate at a speed Nr

due to the torque Td developed in the rotor . Therefore, equation for Pr can be

written as

Pd __ 1rTd / 60

The remaining power, after the mechanical losses Wm are met with, available

in the shaft as mechanical power output Po

Po = Pd – Wm

The mechanical power output Po, which is less than Pd is available in the

shaft

running at a speed of Nr and with a shaft torque T. Therefore the shaft torque

(T) is slightly less than the torque developed Td,

Pd_ __ 1rT / 60

Wm = Pd – Po_ _>_ 1r(Td – T)] / 60

28. Name the tests to be conducted for predetermining the performance of 3-phase

induction machine.

(a) No load test

(b) Blocked rotor test

29. What are the informations obtained from no-load test in a 3-phase I M?

(i) No –load input current per phase,Io

(ii) No load powerfactor and hence no load phase angle

(iii) Iron and mechanical losses together

(iv) elements of equivalent circuit shunt branch

30. What are the informations obtained from blocked rotor test in a 3-phase I M?

(i)Blocked rotor input current per phase at normal voltage

(ii) Blocked rotor power factor and hence phase angle

(iii) Total resistance and leakage reactance per phase of the motor as

refered to the stator

31. What is circle diagram of an I M?

When an I M operates on constant voltage and constant frequency

source,the loci of stator current phasor is found to fall on a circle.This circle

diagram is used to predict the performance of the machine at different loading

conditions as well as mode of operation.

ADDITIONAL UNIV QUESTION 2 MARKS

1. What is the basic principle of a dc generator?

2. What are the basic parts of a dc generator?

3. What is the purpose of yoke in a dc machine?

4. Mention the 2 types of armature winding in a dc machine.

5. What is the function of commutator in a dc generator?

6. Write down the emf equation of a dc generator.

7. What are the different types of dc generators?

8. Draw the circuit diagram of any two types of DC generators.

9. What is the material used for armature core, field winding, commutator amd

brushes?

10. List out the different types of DC motor.

11. Why is a shunt motor called constant speed drive?

12. Define the term “speed regulation” of a DC motor.

13. Write down the torque equation of a DC motor.

14. Give the significance of back emf in a dc motor.

15. Define transformation ratio.

16. Define voltage regulation of a transformer.

17. What are the types of transformers based on construction?

18. What are the different types of single phase induction motor?

19. What are the applications and characteristics of capacitor-start capacitor run

motor?

20. What are the classifications of single phase induction motor based on the method

of starting?

PART – B

1. Explain the principle of operation of a DC generator and derive the emf equation.

Discuss in detail about the construction of DC generator with the neat sketch. (16)

2. Derive the equation for induced emf of a DC machine. (16)

3. Give the significance of back emf in a DC motor. (16)

4. Derive the torque equation of DC motor. (16)

5. Describe the construction details of transformer and also explain the principle of

operation. (16)

6. Explain the principle of operation of single phase 2-winding transformer. (16)

7. Derive the emf equation of a transformer. (16)

8. Explain the principle of operation of single phase induction motor. (16)

9. Explain double field revolving theory. (16)

10.What are the classifications of single phase induction motor based on the

method of starting? (16)

11. A transformer with 40 turns on the high voltage winding is used to step

down the voltage from 240V to 120V. Find the number of turns in the low

voltage winding. (16)

12.A 4 pole, wave wound generator having 40 slots and 10 conductors placed

per slot. The flux per pole is 0.02 wb. Calculate the generated emf when

the generator is drive at 1200 rpm. (16)

13.A 25kw, 250V, dc shunt generator has armature and field resistances of

0.06ohm and 100ohm respectively. Determine the total armature power

developed when working (1) as a generator delivering 25 kw output and

(2) as a motor taking 25kw. (16)

UNIT – III

SEMICONDUCTOR DEVICES AND APPLICATIONS

PART – A (2 MARKS)

1. Define Electronics.

The branch of engineering which deals with conduction of current through

vacuum or gas or a semiconductor.

2. Define Semiconductor .

Semiconductor is a substance has its resistivity in between conductors and

insulators. E.g. silicon, Germanium.

3. Define Conductor

The substances, which allow electric current to pass through them, are

called conductors. E.g. Copper.

4. Define Insulator.

Material, which does not allow the passage of electric current through

them.E.g. Glass, wood, etc.

5. Define Energy band diagram.

It is diagram drawn between inter atomic spacing along the X-axis and the

band energy along the Y-axis.

6. What are free electrons?

The valence electrons, which are very loosely attached to the nucleus, are

known as free electrons.

7. Define doping.

The process of adding impurities to an intrinsic semiconductor is called

doping.

8. Define Intrinsic semiconductor

Semiconductor in an extremely pure form is called intrinsic

semiconductor. Its valence shell must be tetravalent in nature.

9. Define Extrinsic semiconductor

Semiconductor in an impure form is called extrinsic semiconductor. They

are two types (i), P-type (ii), N-type.

10. Define valence band.

The range of energy possessed by valence electron in an atom is called

Valence band.

11. Define Conduction band.

The range of energy possessed by conduction electron in an atom is called

conduction band.

12. Explain forbidden energy gap.

The separation between the conduction band and the valence band on the

energy band diagram.

13. Define P-N junction.

When P-type and N-type are suitably joined together by the conducting

surfaces of these two semiconductors is called P-N junction.

14 Define forward biasing.

When a diode is forward biased the current is produced because the holes

in the P-region and electron from N-region moves towards the junction. The

depletion region formed will be very small hence recombination occurs and

current will be produced.

15. Define reverse biasing.

When a reverse biased voltage is given an electron from N-region and

holes from P-region moves away from the junction,hence the depletion region

formed is very high and hence a small current will be produced due to minority

carriers.

16. Define reverse resistance.

The resistance offered by the diode in its reversed biased condition is

called reverse resistance.

17. Define forward resistance

The resistance offered by the diode in its forward biased condition when a

voltage is given is called forward resistance.

18. Define transition capacitance.

The P-N region on either of the dielectric media act as the plates hence we

have components for making a plate capacitor the junction capacitance is called

transition capacitance.

19. Define power rating.

The power rating of a diode is defined as the maximum value of power

that can be dissipated without failure if Vf is the forward biased voltage and If is

the forward biased current.

Pd= Vf x If.

20. Define diffusion capacitance.

This capacitance effect is present when the junction is forward biased it is

called diffusion capacitance.

21. Define drift velocity and drift current.

When an electric field is applied the charge carriers moves in the opposite

direction and produce current this result is drift current and net average velocity is

called drift velocity.

22. Define transition time.

Only after the minority carriers are swept of the junction the diode voltage

begins to reverse and the diode current decreases exponentially the time which

elapses between and when the diode normally recovered is the called transition

time.

23. Define storage time.

When the conduction diode is reverse biased the voltage doesn’t become

zero. Immediately up to time t1 the diode is conducting in the forward direction.

The time interval t = t2 –t1 during which the stored minority carriers reduces to

zero is called storage time (ts).

24. What is a FET?

a. A field effect transistor is a three terminal semiconductor device in which

current conduction is by one type of carriers (either electrons or holes) and

is controlled by an electric field.

25. Which device is called as unipolar device? Why?

i. Since the operation of FET depends upon the flow of majority

carriers (either the electrons or holes) only, the FET is said to be

unipolar device.

26. What are the main drawbacks in BJT?

i. The main two drawbacks in BJT are

ii. Low input impedance

iii. Considerable noise level.

27. What is pinch off voltage?

i. Drain source voltage above which the drain current become

constant is known as pinch off voltage. The point N is called as

pinch off point. Above the pinch off voltage the channel width

becomes narrow and drain current remains constant.

28. What are advantages of FET?

i. It is a voltage control, constant current driven device that is the

variation in input voltage controls the output current.

ii. The input impedance is very high so it allows a high degree of

isolation between the input and the output circuit.

iii. The carriers are not crossing the junction hence the noise is highly

reduced.

iv. It has a negative temperature co-efficient of resistance. This can

avoid thermal runaway.

29. What are the two types of small signal model?

i. The small signal model is of two types

ii. Low frequency small signal model.

iii. High frequency small signal model.

30. Define transconductance?

a. It is the ratio of change in drain current to the change in gate source

voltage at constant drain source voltage.

31. Define amplification factor?

i. It is the product of drain resistance and transconductance

32. State the two types of MOSFET. State also the modes in which they operate.

i. Types: (a) N- channel MOSFET, (b) P-channel MOSFET

ii. Depletion mode: In this mode the gate is maintained at positive

potential with respect to source.

iii. Enhancement mode: In this mode both the gate and drain are

maintained at positive potential with respect to source.

33. Why the input impedance of FET is more than that of a BJT?

i. The input impedance of FET is more than that of BJT because the

input circuit of FET is reverse biased whereas the input circuit of

BJT is forward biased.

34. What is MOSFET?

i. The MOSFET is an abbreviation for Metal Oxide Semiconductor

Field Effect Transistor. It is a three terminal semiconductor device

similar to FET with gate insulated from the channel.

35. Difference between FET and BJT

FET BJT

1. It is a unipolar device. 1. It is a biopolar device

2. It is a voltage controlled device 2. It is a current driven device

3. Its input resistance is very high. 3. Its input resistance is very low.

4. It is less noisy. 4. It is comparatively more noisy.

5. No thermal runaway 5. There is thermal runaway

6. High switching speed 6. Lower switching speed.

36. Difference between MOSFET and FET

a. FET MOSFET

1. Input impedance is of the order of 10 1. Input impedance is of the order or

2. It is operated only in depletion mode. 2. The depletion MOSFET can be

operated in both depletion mode and

enhancement mode.

3. Gate current is high. 3. Gate current is low.

4. High drain resistance. 4. Higher drain resistance.

37. Difference between UJT and BJT?

a. UJT BJT

1. It has only one PN junction. 1. It has two PN junctions

2. The three terminals are labeled as

Emitter(E), Base1 (B1) and Base2 (B2)

2. The three terminals are labeled as

Emitter (E), Base (B) and Collector(C).

3. It has no ability to amplify signals. 3. It can amplify signals.

38. What is meant by negative resistance region of UJT?

i. In a UJT when the emitter voltage reaches the peak point voltage

(Vp), emitter current starts flowing. After the peak point any effort

to increase in emitter voltage (VE) further leads to sudden increase

in the emitter current with corresponding decrease in VE,

exhibiting negative resistance. This takes place until the valley

point is reached. The region between the peak point and valley

point is called “negative resistance region”.

39. Name the special features of a FET?

High input resistance

Low noise

Better thermal stability

High power gain

High frequency repose.

39. Define voltage variable resistance

i. FET can also be used in the region before pinch off. FET can also

be used as a voltage control resistor. For this operation the drain to

source resistance is controlled by the voltage VGS. Hence it is

called as voltage variable resistor VBR.

40. The noise level in FET is very small. Why?

i. In FET, for current conduction no junction is involved . The

conduction is either through an N- type or P-type semiconductor.

Therefore, the noise level is very small.

ADDITIONAL UNIV 2 MARKS

1. Define electron volt.

2. Define (a) intrinsic semiconductor and (b) extrinsic semiconductor.

3. What is meant by doping in a semiconductor?

4. What are majority and minority carriers in a semiconductor?

5. What are the types of solids based on energy band theory? Give examples for each.

6. Give the energy band description of conductors, semiconductors and insulators.

7. Draw the energy band diagram for an insulating material.

8. What is a zener diode?

9. Define break down voltage in zener diode.

10. How does a PN junction behave under forward and reverse biased condition?

11. Differentiate Avalanche breakdown and zener breakdown.

12. What do you mean by ripple factor?

13. Define peak inverse voltage.

14. What is the peak inverse voltage of centre tapped full wave rectifier?

15. What are the advantages and disadvantages of full wave rectifier?

16. Draw the symbol of npn and pnp transistor.

17. Compare the three transistor configuration with regard to input and output

resistance, current and voltage gain.

18. Calculate IE in a transistor for which β=50 and IB=20μA.

PART – B

1. Explain intrinsic and extrinsic semiconductors with neat diagrams. (16)

2. Describe the working of a PN junction diode with neat diagrams. Also explain its

V-I Characteristics. (16)

3. Explain how a PN junction is formed and state its properties under no bias,

forward bias and reverse bias condition. (16)

4. What is a Zener diode? Explain the operation of Zener diode and draw its

characteristics. (16)

5. Explain the operation of halfwave rectifier with neat sketch. (16)

6. Explain the operation of centre tapped fullwave rectifier with neat diagram. (16)

7. Derive an expression for efficiency of a half-wave rectifier. (16)

8. Explain with a neat diagram how the input and output characteristics of a CE

configuration can be obtained. (16)

9. Compare the input resistance, output resistance and voltage gain of CB, CC and

CE configuration. (16)

10.Explain the working of the CB configuration of a BJT. (16)

11.Explain in detail about small signal CE amplifier. (16)

UNIT – IV

DIGITALS ELECTRONICS

PART – A (2 MARKS)

1. Define binary logic?

Binary logic consists of binary variables and logical operations. The variables

are

designated by the alphabets such as A, B, C, x, y, z, etc., with each variable having

only two

distinct values: 1 and 0. There are three basic logic operations: AND, OR, and NOT.

2. What are the basic digital logic gates?

The three basic logic gates are

AND gate

OR gate

NOT gate

3. What is a Logic gate?

Logic gates are the basic elements that make up a digital system. The

electronic gate

is a circuit that is able to operate on a number of binary inputs in order to perform a

particular logical function.

4.Give the classification of logic families

Bipolar Unipolar

Saturated Non Saturated PMOS

NMOS

CMOS

RTL Schottky TTL

ECL DTL

I I L

TTL

5. Which gates are called as the universal gates? What are its advantages?

The NAND and NOR gates are called as the universal gates. These gates are used to

perform any type of logic application.

6.Classify the logic family by operation?

The Bipolar logic family is classified into

Saturated logic

Unsaturated logic.

The RTL, DTL, TTL, I2L, HTL logic comes under the saturated logic family.

The Schottky TTL, and ECL logic comes under the unsaturated logic family.

7.State the classifications of FET devices.

FET is classified as

1. Junction Field Effect Transistor (JFET)

2. Metal oxide semiconductor family (MOS).

8.Mention the classification of saturated bipolar logic families.

The bipolar logic family is classified as follows:

RTL- Resistor Transistor Logic

DTL- Diode Transistor logic

I2L- Integrated Injection Logic

TTL- Transistor Transistor Logic

ECL- Emitter Coupled Logic

9. Mention the important characteristics of digital IC’s?

Fan out

Power dissipation

Propagation Delay

Noise Margin

Fan In

Operating temperature

Power supply requirements

10. Define Fan-out?

Fan out specifies the number of standard loads that the output of the gate can

drive with out impairment of its normal operation.

11. Define power dissipation?

Power dissipation is measure of power consumed by the gate when fully

driven by allits inputs.

12. What is propagation delay?

Propagation delay is the average transition delay time for the signal to

propagate from input to output when the signals change in value. It is expressed in ns.

13. Define noise margin?

It is the maximum noise voltage added to an input signal of a digital circuit

that does not cause an undesirable change in the circuit output. It is expressed in

volts.

14. Define fan in?

Fan in is the number of inputs connected to the gate without any degradation

in the voltage level.

15. What is Operating temperature?

All the gates or semiconductor devices are temperature sensitive in nature.

The temperature in which the performance of the IC is effective is called as operating

temperature. Operating temperature of the IC vary from 00 C to 700 c.

16.What is High Threshold Logic?

Some digital circuits operate in environments, which produce very high noise

signals.For operation in such surroundings there is available a type of DTL gate

which possesses a high threshold to noise immunity. This type of gate is called HTL

logic or High Threshold Logic.

17. What are the types of TTL logic?

1. Open collector output

2. Totem-Pole Output

3. Tri-state output.

18. What is depletion mode operation MOS?

If the channel is initially doped lightly with p-type impurity a conducting

channel exists at zero gate voltage and the device is said to operate in depletion

mode.

19. What is enhancement mode operation of MOS?

If the region beneath the gate is left initially uncharged the gate field must

induce a channel before current can flow. Thus the gate voltage enhances the channel

current and such a device is said to operate in the enhancement mode.

20. Mention the characteristics of MOS transistor?

1. The n- channel MOS conducts when its gate- to- source voltage is positive.

2. The p- channel MOS conducts when its gate- to- source voltage is negative

3. Either type of device is turned of if its gate- to- source voltage is zero.

21. How schottky transistors are formed and state its use?

A schottky diode is formed by the combination of metal and semiconductor.

The presence of schottky diode between the base and the collector prevents the

transistor from going into saturation. The resulting transistor is called as schottky

transistor.The use of schottky transistor in TTL decreases the propagation delay

without a sacrifice of power dissipation.

22. List the different versions of TTL

1.TTL (Std.TTL) 2.LTTL (Low Power TTL)

3.HTTL (High Speed TTL) 4.STTL (Schottky TTL)

5.LSTTL (Low power Schottky TTL)

23. Why totem pole outputs cannot be connected together.

Totem pole outputs cannot be connected together because such a connection

might produce excessive current and may result in damage to the devices.

24. State advantages and disadvantages of TTL

Adv:

Easily compatible with other ICs

Low output impedance

Disadv:

Wired output capability is possible only with tristate and open collector types

Special circuits in Circuit layout and system design are required.

25. When does the noise margin allow digital circuits to function properly.

When noise voltages are within the limits of VNA(High State Noise Margin)

and VNK for a particular logic family.

26. What happens to output when a tristate circuit is selected for high impedance.

Output is disconnected from rest of the circuits by internal circuitry.

27. What is 14000 series.

It is the oldest and standard CMOS family. The devices are not pin

compatible or electrically compatible with any TTL Series.

28. Define combinational logic

When logic gates are connected together to produce a specified output for

certain specified combinations of input variables, with no storage involved, the

resulting circuit iscalled combinational logic.

29. Explain the design procedure for combinational circuits

The problem definition determine the number of available input variables & required

O/P variables.Assigning letter symbols to I/O variables

Obtain simplified Boolean expression for each O/P.Obtain the logic diagram.

30. Define Half adder and full adder

The logic circuit that performs the addition of two bits is a half adder. The

circuit that performs the addition of three bits is a full adder.

31. Define Decoder?

A decoder is a multiple - input multiple output logic circuit that converts

coded inputs into coded outputs where the input and output codes are different.

32. What is binary decoder?

A decoder is a combinational circuit that converts binary information from n input

lines to a maximum of 2n out puts lines.

33. Define Encoder?

An encoder has 2n input lines and n output lines. In encoder the output lines

generate the binary code corresponding to the input value.

34. What is priority Encoder?

A priority encoder is an encoder circuit that includes the priority function. In

priority encoder, if 2 or more inputs are equal to 1 at the same time, the input having

the highest priority will take precedence.

35. Define multiplexer?

Multiplexer is a digital switch. If allows digital information from several

sources to be routed onto a single output line.

36. What do you mean by comparator

A comparator is a special combinational circuit designed primarily to

compare the relative magnitude of two binary numbers.

ADDITIONAL UNIV 2 MARKS

1. Represent the decimal number 13910 into a binary number.

2. State Demorgan’s theorem

3. Draw the logic symbol and truth table of EX-OR gate.

4. What are universal gates? Why?

5. What is a filp-flop? Where it is used?

6. What are the different types of flip-flops?

7. What is meant by racing in the operation of a flip-flop?

8. State a method to avoid racing problem in JK flip-flop.

9. Mention the types of digital to analog converters.

10. Give the logic diagram and truth table of D flip-flop.

11. What are the different types of counters?

12. What are shift registers?

13. Draw the symbol and truth table of NAND gate.

14. Draw the symbol and truth table of AND gate.

15. Draw the symbol and truth table of NOR gate.

16. Draw the equivalent circuit of NOT gate.

17. Add binary number 1011 and 1110, and write the answer.

18. Convert 1610 into a binary number.

19. Convert the following numbers to decimals. (a) 2378 (b) 23F16

20. Explain the radix of a number system.

PART – B

1. Draw and explain the operation of AND, OR, NOT, NAND and NOR gates with

suitable truth table. (16)

2. How to get NOR from NOT and OR. Also give the truth table for NOR. (16)

3. What are universal gates? Explain their principle of working with

necessary truth table. (16)

4. Design half adder and full adder. (16)

5. Design a full adder and implement it using logic gates. (16)

6. Write short notes on: (16)

a. RS-flip flop b. D-flip flop

c. JK -flip flopd. T-flip flop e. JK-master slave flip flop

7. Briefly explain the working of JK flip flop. (16)

8. Explain the operation of various types of shift register. (16)

9. Explain in details about Analog Digital and Digital to Analog conversion. (16)

10. Explain the operation of RS flip-flop with logic diagram and truth table. (16)

11. With necessary diagrams explain the functioning of any one type of the

following: (16)

a. Decade counter b. D/A converter

12. What is a counter? Discuss briefly about Mod-5 counter. (16)

13. With necessary diagrams explain the functioning of any one type of A/D

converter. (16)

14. Show that NAND and NOR gates are universal building blocks. (16)

15. Describe the operation of a 4-bit binary, ripple counter. (16)

UNIT – V

FUNDAMENTALS OF COMMUNICATION ENGINEERING

PART – A (2 MARKS)

1. Define communication.

Communication is a process of transfer of information bearing signals from one place to another.

2. What do you meant by continuous time signal?It is also refereed as analog signal i.e., the signal is represented continuously in

time.In simple words, a signal x (t) is said to be a continuous time signal if it is defined for time

3. Define digital signal.

A signal define at discrete instants of time' is called a discrete time signal or digital signal.4.. What is modulation?

Modulation is the process of changing some parameter of a high frequency carrier signal accordance with the instantaneous variations of the message signal.

5.Define frequency modulation.

The instantaneous frequency of the caITier is varied linearly with the variations of the age signal while the amplitude of the modulated caITier remains constant.

6.what are the advantages of FM over AM?

*The amplitude of the frequency modulated wave in PM is independent of the depth of modulation.

*, In AM, when the modulation index increases, the total transmission power is increased. In r""'M, the total transmitted power is always same but the bandwidth IS increased with the increased modulation index.

*, By increasing frequency deviation, the noise can further be reduced in FM, whereas AM doesnot have this feature.

* As there is a guard band between PM stations, there is less adjacent channel interference in FM then in AM.

7.What are the disadvantages of FM over AM?

*FM requires a much wider channel, perhaps 7 to 15 times as large as that needed by AM

*FM transmitting and receiving equipments are more complex and expensive.

*Since reception is limited to line of sight, the area of reception for PM is much smaller than for AM.

8. What are the different types of radio receiver? Tuned Radio frequency receiver Super heterodyne receiver.

9. What is the radio transmitter?A radio transmitter is a device that transmits information by means of

radio waves.

10. What is the radio receiver?

A radio receiver is a device that picks up the desired signal from the numerous signals propagating at that time through the atmosphere, amplifies the desired signal to the requisite levels, recovers from it the original modulating signal eventually displays it in the desired manner.

11. What are the advantages of superhetrodyne receiver?1. Improves selectivity interms of adjacent channels.2. Improved receiver stability3. Higher gain per stage4. Uniform bandwidth

12. Define aspect ratio.It is the ratio of width to height of the television picture.

13. What is meant by FAX?

A facsimile or FAX system is a document carrier, with the help of a FAX machine one can send an image on a sheet of paper to another FAX machine over regular telephone lines.

14. What are the application of FAX machine?I. Transmission of photographs

2. Transmission of languages text3. Transmission of document, map etc.

15. What is microwave?

Electromagnetic waves in the frequency range of 1 GHz to 30 GHz are referred to as microwaves’.

16. What is satellite communication system?

A satellite communication is a RF repeater station which has made broadband loin distance communication feasible and ensures a high quality service.

17. What are the sub systems of satellite systems?

The subsystem of satellite communication systems are antenna, transponder, power generation and storage system, telemetry and telecommand sub-system, attitude and orbit control sub-system, propulsion sub system and thermal sub-system.

18. What is the use of optical fibers?

Optical fibers are used for transmission of optical signals in the same manner of co-axial cables for radio wave transmission.

19. What are the application of optical fibre systems?1. International communication2. Inter-city communication3. Inter-exchange communication4. Data links5. Domestic communication6. Plant and traffic control etc.

20. Mention the bandwith frequency of DTH and C-band dish.

Dth-10600 MHz

c-band-5051MHz

PART – B

1. Draw the basic diagram of a wireless communication system and explain. (16)

2. What is meant by modulation? Explain different types of modulation techniques with

neat diagrams. (16)

3. What is meant by amplitude modulation? Explain. Give AM wave equation spectrum

of AM wave. (16)

4. Explain pulse code modulation and show various coding techniques. (16)

5. Explain with neat block diagrams, the principle and working of AM and

FM transmitter. (16)

6. What are the characteristics of a radio receiver? Explain any one radio receiver with a

neat diagram. (16)

7. Explain the working of TV transmitter and receiver. (16)

8. Explain satellite communication system. (16)

9. Explain in details about FAX. (16)

10. Draw the block diagram of optical fibre communication system and explain it. (16)

11. Explain in detail about microwave communication system. (16)

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