Magme Guru: ELECTRICAL ENGINEERING

Showing posts with label ELECTRICAL ENGINEERING. Show all posts

Showing posts with label ELECTRICAL ENGINEERING. Show all posts

Thursday, July 2, 2020

Electrical Circuits MCQs Part 03

ELECTRICAL ENGINEERING July 02, 2020

Electrical Circuits MCQs Part 03

Electrical Circuits MCQs Part 03

21. Two capacitors of capacitance 9 µF and 18 µF in series will have a total capacitance of
A. 27 µF
B. 162 µF
C. 6 µF
D. 180 µF

22. In a series RLC circuit
A. Increasing the frequency decreases the resistance
B. Increasing the frequency increases the resistance
C. Both XL and XC change as frequency changes
D. Impedance will always decrease

23. A series RLC circuit has a ________ power factor at its half-power points
A. Unity
B. Leading
C. Lagging
D. Either B or C

24. Kirchhoff’s laws (KCL and KVL) are applicable to
A. DC circuits
B. AC circuits
C. DC as well as AC circuits
D. Passive networks alone

25. A tank circuit is a
A. Parallel LC circuit
B. Series LC circuit
C. A resonant circuit
D. A non-resonant circuit

26. A capacitive load always has a _________ power facto
A. Leading
B. Lagging
C. Zero
D. Unity

27. What is the temperature coefficient of the resistance Eureka?
A. Infinity
B. Negative
C. Almost zero
D. Positive

28. As applied to a series RLC circuit, bandwidth means
A. The frequency range for maximum power transfer
B. The difference between the highest and lowest frequencies of the oscillator
C. The separation of the half-power points
D. The frequency at which XL = XC

29. Which is considered as the effect of a dielectric material?
A. Increasing capacitance
B. Decreasing capacitance
C. Reducing the working voltage
D. Increasing the distance between the plates

30. The open-circuit voltage at the terminal of load RL is 60V. Under the condition of maximum power transfer, the load voltage will be
A. 60 V
B. 15 V
C. 20 V
D. 30 V

Electrical Circuits MCQs Part 02

ELECTRICAL ENGINEERING July 02, 2020

Electrical Circuits MCQs Part 02

Electrical Circuits MCQs Part 02

11. What is the other name of relative permittivity?
A. Dielectric strength
B. Potential gradient
C. Breakdown voltage
D. Specific inductance capacity
12. In a series RLC circuit
A. The current lags VL by 90˚
B. The current leads VL by 90˚
C. XL leads Xc by 90˚
D. Z = jXL at resonance

13. Resistor with colored bands in the body
A. Wire-wound resistor
B. Carbon-composition resistor
C. Potentiometer
D. Rheostat

14. In a resonant circuit, if Q ≥ 10 resonant frequency __________ bandwidth.
A. Bisects
B. Exceeds
C. Is less than
D. Is equal to

15. Which of the following conditions is not true for a series RLC circuit at resonance?
A. Z = jXL
B. XL = XC
C. The power factor is one
D. The magnitude of Z is √(R^2+〖(XL-XC)〗^2 )

16. The current is ____ times the maximum current at half-power points of a resonance curve.
A. 0.707
B. 1.414
C. 0.5
D. 0.632

17. A gang capacitor is a variable capacitor in which capacitance is varied by changing the
A. Dielectric
B. Number of plates
C. Plate area
D. Distance between plates

18. In an ac circuit with inductive reactance, the
A. Phase angle of the circuit is always 45˚
B. Voltage across the inductance must be 90˚ out-of-phase with the applied voltage
C. Current through the inductance lags its induced voltage by 90˚
D. Current through the inductance and voltage across it are180˚ out-of-phase

19. If three 9 mH inductors are connected in parallel without mutual inductance then the total inductance is
A. 3 mH
B. 9 mH
C. 27 mH
D. 18 mH

20. What is the specific resistance of a pure germanium?
A. 55 Ω-cm
B. 55 Ω -m
C. 5 Ω -mm
D. 55 k Ω -m

Electrical Circuits MCQs Part 01

ELECTRICAL ENGINEERING July 02, 2020

Electrical Circuits MCQs Part 01

Electrical Circuits MCQs Part 01

1. Conventional flow assumes charges flow from
A. Positive to negative
B. Positive to positive
C. Negative to positive
D. Negative to negative

2. Electron flow assumes charges flow from
A. Negative to positive
B. Negative to negative
C. Positive to negative
D. Positive to positive

3. Series resonance occurs when
A. XL = XC
B. XL = R
C. Z = R
D. Both A and C

4. The symbol Q refers to
A. Resonance quotient
B. Quality factor
C. Power quotient
D. Qualification test

5. The ratio of W/VA in an ac circuit means
A. Power factor
B. Reactive factor
C. Quality factor
D. Load factor

6. What is the reciprocal of quality factor?
A. Power factor
B. Reactive factor
C. Dissipation factor
D. 1/Q factor

7. In liquids and gases, ionization current results from a flow of
A. Positive or negative ions
B. Free electrons
C. Ions that are lighter in weight than electrons
D. Protons

8. VL = VC in a series RLC circuit when
A. The value of the impedance is minimum
B. The power factor is zero
C. The current leads the total voltage by 90˚
D. The total voltage is zero

9. At what frequency will an inductor of 5mH have the same reactance as a capacitor of 0.1 µF?
A. 7.12 kHz
B. 7.12 Hz
C. 7.12MHz
D. 7.12 GHz

10. Property of an electric circuit that dissipates electric energy
A. Reactance
B. Impedance
C. Resistance
D. Conductance

Tuesday, April 28, 2020

TEACHING April 28, 2020

DIGITAL ELECTRONICS MCQS PART 09

DIGITAL ELECTRONICS MCQS PART 09

1. The output of a JK flipflop with asynchronous preset and clear inputs is ‘1’. The output can be changed to ‘0’ with one of the following conditions.
(A)By applying J = 0, K = 0 and using a clock.
(B)By applying J = 1, K = 0 and using the clock.
(C)By applying J = 1, K = 1 and using the clock.
(D)By applying a synchronous preset input.
Ans: C Explanation: Preset state of JK Flip-Flop =1
With J=1 K=1 and the clock next state will be complement of the present state.

2. The information in ROM is stored
(A) By the user any number of times.
(B) By the manufacturer during fabrication of the device.
(C) By the user using ultraviolet light.
(D)By the user once and only once.
Ans: B

3. The conversation speed of an analog to digital converter is maximum with the following technique.
(A) Dual slope AD converter.
(B) Serial comparator AD converter.
(C) Successive approximation AD converter.
(D)Parallel comparator AD converter.
Ans: D

4.A weighted resistor digital to analog converter using N bits requires a total of
(A)N precision resistors.
(B) 2N precision resistors.
(C) N + 1 precision resistors.
(D) N – 1 precision resistors.
Ans: A

5. The 2’s complement of the number 1101110 is
(A) 0010001.
(B) 0010001.
(C) 0010010.
(D) None.
Ans: C Explanation: 1’s complement of 1101110 is = 0010001
Thus 2’s complement of 1101110 is = 0010001 + 1 = 0010010

6. The decimal equivalent of Binary number 10101 is
(A) 21
(B) 31
(C) 26
(D) 28
Ans: A Explanation: 1x2^4 + 0x2^3 +1x2^2 +0x2^1 + 1x2^0 = 16 + 0 + 4 + 0 + 1 = 21.

7. How many two input AND gates and two input OR gates are required to realize Y = BD+CE+AB
(A) 1, 1
(B) 4, 2
(C) 3, 2
(D) 2, 3
Ans: A Explanation: There are three product terms, so three AND gates of two inputs are required. As only two input OR gates are available, so two OR gates are required to get the logical sum of three product terms.

8. How many select lines will a 32:1 multiplexer will have
(A) 5.
(B) 8.
(C) 9.
(D) 11.
Ans: A Explanation: For 32 inputs, 5 select lines will be required, as 25 = 32.

DIGITAL ELECTRONICS MCQS PART 08

TEACHING April 28, 2020

DIGITAL ELECTRONICS MCQS PART 08

DIGITAL ELECTRONICS MCQS PART 08

1.How many two-input AND and OR gates are required to realize Y=CD+EF+G
(A) 2,2.
(B) 2,3.
(C) 3,3.
(D) none of these.
Ans: A
Explanation: Y=CD+EF+G
Number of two input AND gates=2
Number of two input OR gates = 2
One OR gate to OR CD and EF and next to OR of G & output of first OR gate.

2. Which of following can not be accessed randomly
(A)DRAM.
(B) SRAM.
(C) ROM.
(D) Magnetic tape.
Ans: D Explanation: Magnetic tape can only be accessed sequentially.

3. The excess-3 code of decimal 7 is represented by
(A) 1100.
(B) 1001.
(C) 1011.
(D) 1010.
Ans: D
Explanation: An excess 3 code is always equal to the binary code +3

4. When an input signal A=11001 is applied to a NOT gate serially, its output signal is
(A) 00111.
(B) 00110.
(C) 10101.
(D) 11001.
Ans: B
Explanation: As A=11001 is serially applied to a NOT gate, first input applied will be LSB 00110.

5. The result of adding hexadecimal number A6 to 3A is
(A)DD.
(B) E0.
(C) F0.
(D) EF.
Ans: B

6. A universal logic gate is one, which can be used to generate any logic function. Which of the following is a universal logic gate?
(A)OR
(B) AND
(C) XOR
(D) NAND
Ans: D
Explanation: NAND can generate any logic function.

7. The logic 0 level of a CMOS logic device is approximately
(A)1.2 volts
(B) 0.4 volts
(C) 5 volts
(D) 0 volts
Ans: D
Explanation: CMOS logic low level is 0 volts approx.

8. Karnaugh map is used for the purpose of
(A)Reducing the electronic circuits used.
(B) To map the given Boolean logic function.
(C)To minimize the terms in a Boolean expression.
(D)To maximize the terms of a given a Boolean expression.
Ans: C

9. A full adder logic circuit will have
(A)Two inputs and one output.
(B)Three inputs and three outputs.
(C) Two inputs and two outputs.
(D) Three inputs and two outputs.
Ans: D Explanation: A full adder circuit will add two bits and it will also accounts the carry input generated in the previous stage. Thus three inputs and two outputs (Sum and Carry) are there.

10. An eight stage ripple counter uses a flip-flop with propagation delay of 75 nanoseconds. The pulse width of the strobe is 50ns. The frequency of the input signal which can be used for proper operation of the counter is approximately
(A)1 MHz.
(B) 500 MHz
(C) 2 MHz.
(D) 4 MHz.
Ans: A
Explanation: Maximum time taken for all flip-flops to stabilize is 75ns x 8 + 50 = 650ns. Frequency of operation must be less than 1/650ns = 1.5 MHz.

DIGITAL ELECTRONICS MCQS PART 07

TEACHING April 28, 2020

DIGITAL ELECTRONICS MCQS PART 07

DIGITAL ELECTRONICS MCQS PART 07

1. How many flip-flops are required to construct mod 30 counter
(A) 5
(B) 6
(C) 4
(D) 8
Ans: A
Explanation: Mod - 30 counter +/- needs 5 Flip-Flop as 30 < 25 Mod - N counter counts total ' N ' number of states.
To count 'N' distinguished states we need minimum n FlipFlop's as [N = 2n] For eg. Mod 8 counter requires 3 Flip-Flop's (8 = 23)

2. How many address bits are required to represent a 32 K memory
(A)10 bits.
(B) 12 bits.
(C) 14 bits.
(D) 16 bits.
Ans: D
Explanation: 32K = 25 x 210 = 215,
Thus 15 address bits are required, Only 16 bits can address it.

3. The number of control lines for 16 to 1 multiplexer is
(A) 2.
(B) 4.
(C) 3.
(D) 5.
Ans: B Explanation: As 16 = 24, 4 Select lines are required.

4. Which of following requires refreshing?
(A)SRAM.
(B) DRAM.
(C) ROM.
(D) EPROM.
Ans: B

5. Shifting a register content to left by one bit position is equivalent to
(A)division by two.
(B) addition by two.
(C) multiplication by two.
(D) subtraction by two.
Ans:C

6. The decimal equivalent of (1100)2 is
(A) 12
(B) 16
(C) 18
(D) 20
Ans: A
Explanation: (1100)2 = (12)10

7. The binary equivalent of (FA)16 is
(A) 1010 1111
(B) 1111 1010
(C) 10110011
(D) none of these
Ans: B
Explanation: (FA)16 = (11111010)10

8.The output of SR flip flop when S=1, R=0 is
(A) 1
(B) 0
(C) No change
(D) High impedance
Ans: A
Explanation: As for the SR flip-flop S=set input R=reset input ,when S=1, R=0, Flip-flop will be set.

9. The number of flip flops contained in IC 7490 is
(A) 2.
(B) 3.
(C) 4.
(D) 10.
Ans: A

10. The number of control lines for 32 to 1 multiplexer is
(A) 4.
(B) 5
(C) 16.
(D) 6.
Ans: B
Explanation: The number of control lines for 32 (25) and to select one input among them total 5 select lines are required.

DIGITAL ELECTRONICS MCQS PART 06

TEACHING April 28, 2020

DIGITAL ELECTRONICS MCQS PART 06

DIGITAL ELECTRONICS MCQS PART 06

1. Using complement method negative numbers can also be subtracted.
In a positive logic system, logic state 1 corresponds to
(A)positive voltage
(B) higher voltage level
(C) zero voltage level
(D) lower voltage level
Ans: B

2. We decide two voltages levels for positive digital logic. Higher voltage represents logic 1 & a lower voltage represents logic 0. The commercially available 8-input multiplexer integrated circuit in the TTL family is
(A) 7495.
(B) 74153.
(C) 74154.
(D) 74151.
Ans: B
Explanation: MUX integrated circuit in TTL is 74153.

3. CMOS circuits are extensively used for ON-chip computers mainly because of their extremely
(A)low power dissipation.
(B) high noise immunity.
(C) large packing density.
(D) low cost.
Ans: C
Explanation: Because CMOS circuits have large packing density.

4.The MSI chip 7474 is
(A) Dual edge triggered JK flip-flop (TTL).
(B)Dual edge triggered D flip-flop (CMOS).
(C)Dual edge triggered D flip-flop (TTL).
(D) Dual edge triggered JK flip-flop (CMOS).
Ans: C
Explanation: MSI chip 7474 dual edge triggered D Flip-Flop.

5. Which of the following memories stores the most number of bits
(A)a 5M× 8 memory.
(B) a 1M × 16 memory.
(C) a 5M × 4 memory.
(D) a 1M ×12 memory.
Ans: A
Explanation: 5Mx8 = 5 x 220 x 8 = 40M (max)

6. The process of entering data into a ROM is called
(A)burning in the ROM
(B) programming the ROM
(C) changing the ROM
(D) charging the ROM
Ans: B
Explanation: The process of entering data into ROM is known as programming the ROM.

7. When the set of input data to an even parity generator is 0111, the output will be
(A) 1
(B) 0
(C) Unpredictable
(D) Depends on the previous input
Ans: B
Explanation: In even parity generator if number of 1 is odd then output will be zero.

8. The number 140 in octal is equivalent to
(A) (96)10
(B) (86)10
(C) (90)10
(D) none of these
Ans: A
Explanation: (140)8 = (96)10
1 x 8^2 + 4 x 8 + 0x 1 = 64 + 32 = 96

9. The NOR gate output will be low if the two inputs are
(A) 00
(B) 01
(C) 10
(D) 11
(E) B,C,and D
Ans: E
Explanation: O/P is low if any of the I/P is high

10.Which of the following is the fastest logic?
(A)ECL
(B) TTL
(C) CMOS
(D) LSI
Ans: A

DIGITAL ELECTRONICS MCQS PART 05

TEACHING April 28, 2020

DIGITAL ELECTRONICS MCQS PART 05

DIGITAL ELECTRONICS MCQS PART 05

1.How many select lines will a 16 to 1 multiplexer will have
(A) 4
(B) 3
(C) 5
(D) 1
Ans: A Explanation: In 16 to 1 MUX four select lines will be required to select 16 ( 24 ) inputs.

2. How many address bits are required to represent 4K memory
(A) 5 bits.
(B) 12 bits.
(C) 8 bits.
(D) 10 bits.
Ans: B Explanation: For representing 4K memory, 12 address bits are required as
    4K = 22 x 210 = 212     (1K = 1024 = 210)

3. For JK flipflop J = 0, K=1, the output after clock pulse will be
(A) 1.
(B) no change.
(C) 0.
(D) high impedance.
Ans: C
Explanation: J=0, K=1, these inputs will reset the flip-flop after the clock pulse. So whatever be the previous output, the next state will be 0.

4. Which of following are known as universal gates
(A)NAND & NOR.
(B) AND & OR.
(C) XOR & OR.
(D) None.
Ans: A
Explanation: NAND & NOR are known as universal gates, because any digital circuit can be realized completely by using either of these two gates.

5. Which of the following memories stores the most number of bits
(A)64K × 8 memory.
(B) 1M × 8 memory.
(C) 32M × 8 memory.
(D) 64 × 6 memory.
Ans: C
Explanation: 32M x 8 stores most number of bits
25 x 220   = 225     (1M = 220 = 1K x 1K = 210 x 210)

6. How many flip flops are required to construct a decade counter
(A) 10
(B) 3
(C) 4
(D) 2
Ans: C Explanation: Decade counter counts 10 states from 0 to 9 ( i.e. from 0000 to 1001 ) Thus four FlipFlop's are required.

7. Which TTL logic gate is used for wired ANDing
(A)Open collector output
(B) Totem Pole
(C) Tri state output
(D) ECL gates
Ans: A
Explanation: Open collector output.

8. CMOS circuits consume power
(A) Equal to TTL
(B) Less than TTL
(C) Twice of TTL
(D) Thrice of TTL
Ans: B
Explanation: As in CMOS one device is ON & one is Always OFF so power consumption is low.

9. In a RAM, information can be stored
(A) By the user, number of times.
(B) By the user, only once.
(C) By the manufacturer, a number of times.
(D) By the manufacturer only once.
Ans: A
Explanation: RAM is used by the user, number of times.

10. The chief reason why digital computers use complemented subtraction is that it
(A)Simplifies the circuitry.
(B) Is a very simple process.
(C) Can handle negative numbers easily.
(D)Avoids direct subtraction.
Ans: C

DIGITAL ELECTRONICS MCQS PART 04

TEACHING April 28, 2020

DIGITAL ELECTRONICS MCQS PART 04

DIGITAL ELECTRONICS MCQS PART 04

1. When signed numbers are used in binary arithmetic, then which one of the following notations would have unique representation for zero.
(A)Sign-magnitude.
(B) 1’s complement.
(C) 2’s complement.
(D) 9’s complement.
Ans: A

2. Which of following consume minimum power
(A)TTL.
(B) CMOS.
(C) DTL.
(D) RTL.
Ans: B
Explanation: CMOS consumes minimum power as in CMOS one p-MOS & one n-MOS transistors are connected in complimentary mode, such that one device is ON & one is OFF.

3. In digital ICs, Schottky transistors are preferred over normal transistors because of their
(A)Lower Propagation delay.
(B) Higher Propagation delay.
(C) Lower Power dissipation.
(D) Higher Power dissipation.
Ans: A
Explanation: Lower propagation delay as shottky transistors reduce the storage time delay by preventing the transistor from going deep into saturation.

4. The following switching functions are to be implemented using a Decoder:
f1 =)m(1, 2, 4, 8,10,14) f2 =) m(2, 5, 9,11) f3 =) m(2, 4, 5, 6, 7)
The minimum configuration of the decoder should be
(A) 2 – to – 4 line.
(B) 3 – to – 8 line.
(C) 4 – to – 16 line.
(D) 5 – to – 32 line.
Ans: C
Explanation: 4 to 16 line decoder as the minterms are ranging from 1 to 14.

5. A 4-bit synchronous counter uses flip-flops with propagation delay times of 15 ns each. The maximum possible time required for change of state will be
(A) 15 ns.
(B) 30 ns.
(C) 45 ns.
(D) 60 ns.
Ans: A
Explanation: 15 ns because in synchronous counter all the flip-flops change state at the same time.

6. Words having 8-bits are to be stored into computer memory. The number of lines required for writing into memory are
(A) 1.
(B) 2.
(C) 4.
(D) 8.
Ans: D
Explanation: Because 8-bit words required 8 bit data lines.

7.The decimal equivalent of Binary number 11010 is
(A) 26.
(B) 36.
(C) 16.
(D) 23.
Ans: A Explanation: 11010 = 1 X 24 + 1 X 2 3 + 0 X 22 + 1 X 21 = 26

8. 1’s complement representation of decimal number of -17 by using 8 bit representation is
(A) 1110 1110
(B) 1101 1101
(C) 1100 1100
(D) 0001 0001
Ans: A
Explanation: (17)10 = (10001)2
In 8 bit = 00010001
1's Complement = 11101110

9.The excess 3 code of decimal number 26 is
(A) 0100 1001
(B) 01011001
(C) 1000 1001
(D) 01001101
Ans: B
Explanation: (26)10 in BCD is ( 00100110 ) BCD
Add 011 to each BCD 01011001 for excess – 3

10.How many AND gates are required to realize Y = CD+EF+G
(A) 4
(B) 5
(C) 3
(D) 2
Ans: D
Explanation: To realize Y = CD + EF + G
Two AND gates are required (for CD & EF).

DIGITAL ELECTRONICS MCQS PART 03

TEACHING April 28, 2020

DIGITAL ELECTRONICS MCQS PART 03

DIGITAL ELECTRONICS MCQS PART 03

1. Which of the following is the fastest logic
(A)TTL
(B) ECL
(C) CMOS
(D) LSI
Ans: B
ECL is the fastest logic family of all logic families.
(High speeds are possible in ECL because the transistors are used in difference amplifier configuration, in which they are never driven into saturation and thereby the storage time is eliminated.

2.If the input to T-flipflop is 100 Hz signal, the final output of the three T-flipflops in cascade is
(A) 1000 Hz
(B) 500 Hz
(C) 333 Hz
(D) 12.5 Hz.
Ans: D

3. Which of the memory is volatile memory
(A)ROM
(B) RAM
(C) PROM
(D) EEPROM
Ans: B
Explanation: RAM is a volatile memory (Volatile memory means the contents of the RAM get erased as soon as the power goes off.)

4. -8 is equal to signed binary number
(A) 10001000
(B) 00001000
(C) 10000000
(D) 11000000
Ans: A
Explanation: 8 is equal to signed binary number 10001000

5. DeMorgan’s first theorem shows the equivalence of
(A)OR gate and Exclusive OR gate.
(B)NOR gate and Bubbled AND gate.
(C)NOR gate and NAND gate.
(D)NAND gate and NOT gate
Ans: B

6. The digital logic family which has the lowest propagation delay time is
(A)ECL
(B) TTL
(C) CMOS
(D) PMOS
Ans: A
Explanation: The digital logic family which has the lowest propagation delay time is ECL (Lowest propagation delay time is possible in ECL because the transistors are used in difference amplifier configuration, in which they are never driven into saturation and thereby the storage time is eliminated).

7. The device which changes from serial data to parallel data is
(A)COUNTER
(B) MULTIPLEXER
(C) DEMULTIPLEXER
(D) FLIP-FLOP
Ans: C
Explanation: The device which changes from serial data to parallel data is demultiplexer. (A demultiplexer takes in data from one line and directs it to any of its N outputs depending on the status of the select inputs.)

8. A device which converts BCD to Seven Segment is called
(A)Encoder
(B) Decoder
(C) Multiplexer
(D) Demultiplexer
Ans: B
Explanation: device which converts BCD to Seven Segment is called DECODER. (A decoder coverts binary words into alphanumeric characters.)

9.The access time of ROM using bipolar transistors is about
(A)1 sec
(B) 1 msec
(C) 1 µsec
(D) 1 nsec.
Ans: C
Explanation: The access time of ROM using bipolar transistors is about 1 µ sec.

10. The A/D converter whose conversion time is independent of the number of bits is
(A)Dual slope
(B) Counter type
(C) Parallel conversion
(D) Successive approximation.
Ans: C
Explanation: The A/D converter whose conversion time is independent of the Number of bits is Parallel conversion.
(This type uses an array of comparators connected in parallel and comparators compare the input voltage at a particular ratio of the reference voltage).

DIGITAL ELECTRONICS MCQS PART 02

TEACHING April 28, 2020

DIGITAL ELECTRONICS MCQS PART 02

DIGITAL ELECTRONICS MCQS PART 02

1.The Gray code for decimal number 6 is equivalent to
(A) 1100
(B) 1001
(C) 0101
(D) 0110
Ans: C

2. The digital logic family which has minimum power dissipation is
(A) TTL
(B) RTL
(C) DTL
(D) CMOS
Ans: D
Explanation: The digital logic family which has minimum power dissipation is CMOS.
(CMOS being an unipolar logic family, occupy a very small fraction of silicon Chip area)

3. The output of a logic gate is 1 when all its inputs are at logic 0. the gate is either
(A) a NAND or an EX-OR
(B) an OR or an EX-NOR
(C) an AND or an EX-OR
(D) a NOR or an EX-NOR
Ans: D

4. Data can be changed from special code to temporal code by using
(A) Shift registers
(B) counters
(C) Combinational circuits
(D) A/D converters.
Ans: A
Explanation: Data can be changed from special code to temporal code by using Shift Registers. (A Register in which data gets shifted towards left or right when clock pulses are applied is known as a Shift Register.

5. A ring counter consisting of five Flip-Flops will have
(A)5 states
(B) 10 states
(C) 32 states
(D) Infinite states.
Ans: A
Explanation: A ring counter consisting of Five Flip-Flops will have 5 states.

6. The 2’s complement of the number 1101101 is
(A) 0101110
(B) 0111110
(C) 0110010
(D) 0010011
Ans: D
Explanation: The 2’s complement of the number 1101101 is 0010011
(1’s complement of the number 1101101 is 0010010
2’s complement of the number 1101101is 0010010 + 1 =0010011)

7. The correction to be applied in decimal adder to the generated sum is
(A) 00101
(B) 00110
(C) 01101
(D) 01010
Ans: B
Explanation: The correction to be applied in decimal adder to the generated sum is 00110.
When the four bit sum is more than 9 then the sum is invalid. In such cases, add +6(i.e. 0110) to the four bit sum to skip the six invalid states. If a carry is generated when adding 6, add the carry to the next four bit group .

8. When simplified with Boolean Algebra (x + y)(x + z) simplifies to
(A)x
(B) x + x(y + z)
(C) x(1 + yz)
(D) x + yz
Ans: D

9.The excess 3 code of decimal number 26 is
(A) 0100 1001
(B) 01011001
(C) 1000 1001
(D) 01001101
Ans: B
(26)10 in BCD is ( 00100110 ) BCD
Add 011 to each BCD 01011001 for excess – 3

10. The code where all successive numbers differ from their preceding number by single bit is
(A)Binary code.
(B) BCD.
(C) Excess – 3.
(D) Gray.
Ans: D
The code where all successive numbers differ from their preceding number by single bit is Gray Code.
(It is an unweighted code. The most important characteristic of this code is that only a single bit change occurs when going from one code number to next.)

DIGITAL ELECTRONICS MCQS PART 01

TEACHING April 28, 2020

DIGITAL ELECTRONICS MCQS PART 01

DIGITAL ELECTRONICS MCQS PART 01

1. The NAND gate output will be low if the two inputs are
(A) 00
(B) 01
(C) 10
(D) 11
Ans: D

2.What is the binary equivalent of the decimal number 368
(A) 101110000
(B) 110110000
(C) 111010000
(D) 111100000
Ans: A

3. The decimal equivalent of hex number 1A53 is
(A)6793
(B) 6739
(C) 6973
(D) 6379
Ans: B

4. (734)8 = ( )16
(A) C 1 D
(B) D C 1
(C) 1 C D
(D) 1 D C
Ans: D

5. The simplification of the Boolean expression (ABC)+ (ABC) is
(A) 0
(B) 1
(C) A
(D) BC
Ans: B

6. The number of control lines for a 8 – to – 1 multiplexer is
(A) 2
(B) 3
(C) 4
(D) 5
Ans: B
7. How many Flip-Flops are required for mod–16 counter?
(A) 5
(B) 6
(C) 3
(D) 4
Ans: D

8. EPROM contents can be erased by exposing it to
A. Ultraviolet rays.
B.Infrared rays.
C. Burst of microwaves.
D.Intense heat radiations
Ans: A

10. The hexadecimal number ‘A0’ has the decimal value equivalent to
(A) 80
(B) 256
(C) 100
(D) 160
Ans: D

Monday, April 20, 2020

TRANSFORMER MCQS SET 34

Transformers April 20, 2020

TRANSFORMER MCQS SET 34

TRANSFORMER MCQS SET 34

1. Which of the following loss in a transformer is zero even at full load ?
(a) Core loss (b) Friction loss (c) Eddy current loss
(d) Hysteresis loss
Ans: b

2. Which of the following is the most likely source of harmonics in a transformer ?
(a) poor insulation (b) Overload (c) loose connections
(d) Core saturation
Ans: d

3. If a transformer is continuously operated the maximum temperature rise will occur in
(a) core (b) windings (c) tank (d) any of the above
Ans: b

4. The hum in a transformer is mainly attributed to
(a) load changes (b) oil in the transformer
(c) magnetostriction (d) mechanical vibrations
Ans: c

5. The maximum load that a power transformer can carry is limited by its
(a) temperature rise (b) dielectric strength of oil
(c) voltage ratio (d) copper loss
Ans: c

6. The efficiency of a transformer, under heavy loads, is comparatively low because
(a) copper loss becomes high in proportion to the output
(b) iron loss is increased considerably
(c) voltage drop both in primary and secondary becomes large
(d) secondary output is much less as compared to primary input

Ans: a

7. An open-circuit test on a transformer is conducted primarily to measure
(a) insulation resistance (b) copper loss (c) core loss
(d) total loss (e) efficiency (f) none of the above
Ans: c

8. A no-load test is performed on a transformer to determine
(a) core loss (b) copper loss (c) efficiency
(d) magnetising current (e) magnetising current and loss
Ans: e

9. The voltage transformation ratio of a transformer is equal to the ratio of
(a) primary turns to secondary turns
(b) secondary current to primary current
(c) secondary induced e.m.f. to primary induced e.m.f.
(d) secondary terminal voltage to primary applied voltage
Ans: c

10. Part of the transformer which is most subject to damage from overheating is
(a) iron core (b) copper winding (c) winding insulation
(d) frame or case (e) transformer tank
Ans: c

11. If a transformer is switched on to a voltage more than the rated voltage
(a) its power factor will deteriorate
(b) its power factor will increase
(c) its power factor will remain unaffected
(d) its power factor will be zero
Ans: a

12. Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is
(a) approximately equal to one (b) less than one
(c) great than one (d) none of the above
Ans: a

13. Minimum voltage regulation occurs when the power factor of the load is
(a) unity (b) lagging (c) leading (d) zero
Ans: c

14. In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of
(a) less than 15 A (b) more than 15 A (c) 15 A (d)
Ans: a

15. The efficiencies of transformers compared with that of electric motors of the same power are
(a) about the same (6) much smaller (c) much higher
(d) somewhat smaller (e) none of the above
Ans: c

TRANSFORMER MCQS SET 33

Transformers April 20, 2020

TRANSFORMER MCQS SET 33

TRANSFORMER MCQS SET 33

1. The secondary of a current transformer is always short-circuited under operating conditions because it
(a) avoids core saturation and high voltage induction
(b) is safe to human beings (c) protects the primary circuit
(d) none of the above
Ans: a

2. In a transformer the resistance between its primary and secondary should be
(a) zero (b) 10 Q (c) 1000 Q (d) infinity
Ans: d

3. A good voltage regulation of a transformer means
(a) output voltage fluctuation from no load to full load is least
(b) output voltage fluctuation with power factor is least
(c) difference between primary and secondary voltage is least
(d) difference between primary and secondary voltage is maximum

Ans: a

4. For a transformer, operating at constant load current, maximum efficiency will occur at
(a) 0.8 leading power factor (b) 0.8 lagging power factor
(c) zero power factor (d) unity power factor
Ans: d

5. Which of the following protection is normally not provided on small distribution transformers ?
(a) Overfluxing protection (b) Buchholz relay
(c) Overcurrent protection (d) All of the above
Ans: b

6. Which of the following acts as a protection against high voltage surges due to lightning and switching ?
(a) Horn gaps (b) Thermal overload relays
(c) Breather (d) Conservator
Ans: a

7. The efficiency of two identical transformers under load conditions can be determined by
(a) short-circuit test (b) back-to-back test
(c) open circuit test (d) any of the above
Ans: b

8. Which of the following insulating materials can withstand the highest temperature safely ?
(a) Cellulose (b) Asbestos (c) Mica (d) Glass fibre
Ans: c

9. Which of the following parts of a transformer is visible from outside ?
(a) Bushings (b) Core (c) Primary winding
(d) Secondary winding
Ans: a

10. The noise produced by a transformer is termed as
(a) zoom (b) hum (c) ringing (d) buzz
Ans: b

TRANSFORMER MCQS SET 32

Transformers April 20, 2020

TRANSFORMER MCQS SET 32

TRANSFORMER MCQS SET 32

1. A shell-type transformer has
(a) high eddy current losses (b) reduced magnetic leakage
(c) negligibly hysteresis losses (d) none of the above
Ans: b

2. A transformer can have regulation closer to zero
(a) on full-load (b) on overload (c) on leading power factor
(d) on zero power factor
Ans: c

3. A transformer transforms
(a) voltage (b) current (c) current and voltage (d) power

Ans: d

4. Which of the following is not the standard voltage for power supply in India ?
(a) llkV (b) 33kV (c) 66 kV (d) 122 kV
Ans: d

5. Reduction in core losses and increase in permeability are obtained with transformer employing
(a) core built-up of laminations of cold rolled grain oriented steel
(b) core built-up of laminations of hot rolled sheet
(c) either of the above
(d) none of the above
Ans: a

6. In a power or distribution transformer about 10 per cent end turns are heavily insulated
(a) to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns
(b) to absorb the line surge voltage and save the winding of transformer from damage
(c) to reflect the line surge and save the winding of a transformer from damage
(d) none of the above
Ans: a

7. For given applied voltage, with the increase in frequency of the applied voltage
(a) eddy current loss will decrease
(b) eddy current loss will increase
(c) eddy current loss will remain unchanged
(d) none of the above
Ans: c

8. Losses which occur in rotating electric machines and do not occur in trans formers are
(a) friction and windage losses
(b) magnetic losses
(c) hysteresis and eddy current losses
(d) copper losses
Ans: a

9. In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are
(a) hysteresis and eddy current losses
(b) friction and windage losses
(c) copper losses (d) none of the above
Ans: a

10. Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and
drawing a current of 10 A from 200 V A.C. supply is incorrect ?
(a) Its secondary current is 5 A (b) Its secondary voltage is 400 V
(c) Its rating is 2 kVA (d) Its secondary current is 20 A
(e) It is a step-up transformer
Ans: d

TRANSFORMER MCQS SET 31

Transformers April 20, 2020

TRANSFORMER MCQS SET 31

TRANSFORMER MCQS SET 31

1. Which type of winding is used in 3phase shell-type transformer?
(a) Circular type (b) Sandwich type (c) Cylindrical type
(d) Rectangular type
Ans: b

2. During open circuit test of a transformer
(a) primary is supplied rated voltage
(b) primary is supplied full-load current
(c) primary is supplied current at reduced voltage
(d) primary is supplied rated kVA
Ans: a

3. Open circuit test on transformers is conducted to determine
(a) hysteresis losses (b) copper losses
(c) core losses (d) eddy current losses
Ans: c

4. Short circuit test on transformers is conducted to determine
(a) hysteresis losses (b) copper losses
(c) core losses (d) eddy current losses
Ans: b

5. For the parallel operation of single phase transformers it is necessary that they should have
(a) same efficiency (b) same polarity (c) same kVA rating
(d) same number of turns on the secondary side.
Ans: b

6. The transformer oil should have volatility and viscosity.
(a) low,low (b) high,high (c) low,high (d) high,low
Ans: a

7. The function of breather in a transformer is
(a) to provide oxygen inside the tank
(b) to cool the coils during reduced load
(c) to cool the transformer oil
(d) to arrest flow of moisture when outside air enters the transformer
Ans: d

8. The secondary winding of which of the following transformers is always kept closed ?
(a) Step-up transformer (b) Step-down transformer
(c) Potential transformer (d) Current transformer
Ans: d

9. The size of a transformer core will depend on
(a) frequency (b) area of the core
(c) flux density of the core material (d) (a) and (b) both
Ans: d

10. N atural air coo ling is generally restricted for transformers up to
(a) 1.5 MVA (b) 5 MVA (c) 15 MVA (d) 50 MVA
Ans: a

TRANSFORMER MCQS SET 30

Transformers April 20, 2020

TRANSFORMER MCQS SET 30

TRANSFORMER MCQS SET 30

1. The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer
(a) Conservator (b) Breather (c) Bushings (d) Buchholz relay

Ans: a

2. An ideal transformer is one which has
(a) no losses and magnetic leakage
(b) interleaved primary and secondary windings
(c) a common core for its primary and secondary windings
(d) core of stainless steel and winding of pure copper metal
(e) none of the above
Ans: a

3. When a given transformer is run at its rated voltage but reduced frequency, its
(a) flux density remains unaffected (b) iron losses are reduced
(c) core flux density is reduced (d) core flux density is increased

Ans: d

4. In an actual transformer the iron loss remains practically constant from noload to fullload because
(a) value of transformation ratio remains constant
(b) permeability of transformer core remains constant
(c) core flux remains practically constant
(d) primary voltage remains constant
(c) secondary voltage remains constant
Ans: c

5. An ideal transformer will have maximum efficiency at a load such that
(a) copper loss = iron loss (b) copper loss < iron loss
(c) copper loss > iron loss (d) none of the above
Ans: a

6. If the supply frequency to the transformer is increased,"the iron loss will
(a) not change (b) decrease (c) increase (d) any of the above

Ans: c

7. Negative voltage regulation is indicative that the load is
(a) capacitive only (b) inductive only
(c) inductive or resistive (d) none of the above
Ans: a

8. Iron loss of a transformer can be measured by
(a) low power factor wattmeter (b) unity power factor wattmeter
(c) frequency meter (d) any type of wattmeter
Ans: a

9. When secondary of a current transformer is open-circuited its iron core will be
(a) hot because of heavy iron losses taking place in it due to high flux density
(b) hot because primary will carry heavy current
(c) cool as there is no secondary current
(d) none of above will happen
Ans: a

10. The transformer laminations are insulated from each other by
(a) mica strip (6) thin coat of varnish
(c) paper (d) any of the above
Ans: b

TRANSFORMER MCQS SET 29

Transformers April 20, 2020

TRANSFORMER MCQS SET 29

TRANSFORMER MCQS SET 29

1. Harmonics in transformer result in
(a) increased core losses (b) increased I2R losses
(c) magnetic interference with communication circuits (d) all
Ans: d

2. The core used in high frequency transformer is usually
(a) copper core (b) cost iron core
(c) air core (d) mild steel core
Ans: c

3. The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be
(a) 6400 W (b) 1600 W (c) 800 W (d) 400 W
Ans: d

4. The value of flux involved m the e.m.f. equation of a transformer is
(a) average value (b) r.m.s. value (c) maximum value
(d) instantaneous value
Ans: c

5. Silicon steel used in laminations mainly reduces
(a) hysteresis loss (b) eddy current losses
(c) copper losses (d) all of the above
Ans: a

6. Which winding of the transformer has less cross-sectional area?
(a) Primary winding (b) Secondary winding
(c) Low voltage winding (d) High voltage winding
Ans: d

7. Power transformers are generally designed to have maximum efficiency around
(a) no-load (b) half-load (c) near full-load (d) 10% overload

Ans: c

8. Which of the following is the main advantage of an auto-transformer over a two winding transformer ?
(a) Hysteresis losses are reduced
(b) Saving in winding material
(c) Copper losses are negligible
(d) Eddy losses are totally eliminated
Ans: b

9. During short circuit test iron losses are negligible because
(a) the current on secondary side is negligible
(b) the voltage on secondary side does not vary
(c) the voltage applied on primary side is low
(d) full-load current is not supplied to the transformer
Ans: c

10. Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in
(a) short-circuiting of the secondaries
(b) power factor of one of the trans¬formers is leading while that of the other lagging
(c) transformers having higher copper losses will have negligible core losses
(d) loading of the transformers not in proportion to their kVA ratings

Ans: d

TRANSFORMER MCQS SET 28

Transformers April 20, 2020

TRANSFORMER MCQS SET 28

TRANSFORMER MCQS SET 28

1. Buchholz's relay gives warning and protection against
(a) electrical fault inside the transformer itself
(b) electrical fault outside the transformer in outgoing feeder
(c) for both outside and inside faults
(d) none of the above
Ans: a

2. The magnetising current of a transformer is usually small because it has
(a) small air gap (b) large leakage flux
(c) laminated silicon steel core (d) fewer rotating parts
Ans: a

3. Which of the following does not change in an ordinary transformer ?
(a) Frequency (b) Voltage (c) Current (d) Any of the above

Ans: a

4. Which of the following properties is not necessarily desirable for the material for transformer core ?
(a) Low hysteresis loss (b) High permeability
(c) High thermal conductivity (d) Adequate mechanical strength

Ans: c

5. The leakage flux in a transformer depends upon
(a) load current (b) load current and voltage
(c) load current, voltage and frequency
(d) load current, voltage, frequency and power factor
Ans: a

6. The path of the magnetic flux in transformer should have
(a) high reluctance (b) low reactance
(c) high resistance (d) low resistance
Ans: b

7. Noise level test in a transformer is a
(a) special test (b) routine test (c) type test (d) none
Ans: c

8. Which of the foJIowing is not a routine test on transformers ?
(a) Core insulation voltage test (b) Impedance test
(c) Radio interference test (d) Polarity test
Ans: c

9. A transformer can have zero voltage regulation at
(a) leading power factor (b) lagging power factor
(c) unity power factor (d) zero power factor
Ans: a

10. Helical coils can be used on
(a) low voltage side of high kVA trans¬formers
(b) high frequency transformers
(c) high voltage side of small capacity transformers
(d) high voltage side of high kVA rating transformers
Ans: a

TRANSFORMER MCQS SET 27

Transformers April 20, 2020

TRANSFORMER MCQS SET 27

TRANSFORMER MCQS SET 27

1. The highest voltage for transmitting electrical power in India is
(a) 33 kV. (6) 66 kV (c) 132 kV (d) 400 kV
Ans: d

2. In a transformer the resistance between its primary and secondary is
(a) zero (b) 1 ohm (c) 1000 ohms (d) infinite
Ans: d

3. A transformer oil must be free from
(a) sludge (b) odour (c) gases (d) moisture
Ans: d

4. A Buchholz relay can be installed on
(a) auto-transformers (b) air-cooled transformers
(c) welding transformers (d) oil cooled transformers
Ans: d

5. Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds
(a) 50°C (b) 80°C (c) 100°C (d) 150°C
Ans: d

6. The main reason for generation of harmonics in a transformer could be
(a) fluctuating load                (b) poor insulation
(c) mechanical vibrations            (d) saturation of core
Ans: d
7. Distribution transformers are generally designed for maximum efficiency around
(a) 90% load          (b) zero load          (c) 25% load       (d) 50% load

Ans: d

8. Which of the following property is not necessarily desirable in the material for transformer core?
(a) Mechanical strength (b) Low hysteresis loss
(c) High thermal conductivity (d) High permeability
Ans: c

9. Star/star transformers work satisfactorily when
(a) load is unbalanced only (b) load is balanced only
(c) on balanced as well as unbalanced loads
(d) none of the above
Ans: b

10. Delta/star transformer works satisfactorily when
(a) load is balanced only (b) load is unbalanced only
(c) on balanced as well as unbalanced loads
(d) none of the above
Ans: c

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