MPPGCL JE Electronics Mock Test - 7 - Electronics and Communication Engineering (ECE) MCQ

The non-linear device acts as frequency multiplier with appropriate bandpass filter, since y(t) = [x(t)]³ is the non-linear device, 3^rd harmonic with carrier frequency is possible i.e. f_C = 32.4 MHz

The frequency deviation in a phase-modulated carrier is proportional to the amplitude and frequency of the modulating signal both.

Derivation:

A general expression for a phase-modulated wave is:

xPM (t) = A cos [2πfct + kpm(t)]

The instantaneous angle is given as:

ϕi(t) = 2πfct + kp m(t)

The instantaneous frequency (in Hz) will be obtained as:

Frequency deviation is given by:

For a single tone modulation:

m(t) = Am sin ωmt

The frequency deviation becomes:

Δf ∝ Am fm

Concept :

For a signal x(t) sampled with a sampling interval T_s, the discrete sequence can be written as:

T_s = sampling interval

Analysis:

x(t) = 3 cos 100 πt

f_s = 200 Hz, T_s = 1/200 = 0.005 sec

x(n) = 3 cos 100π(n/200)

x(n) = 3 cos (πn/2)

Concept:

Johnson counter also known as creeping counter is an example of a synchronous counter.

In the Johnson counter, the complemented output of the last flip-flop is connected to an input of the first flip-flop, and to implement an n-bit Johnson counter we require n flip-flop.

Analysis:

The circuit diagram can be simplified at the block level as shown below

The initial state is given as 0000

After the 6th Clock, ABCD will be at 0011

Junction Built-in voltage:

V₀ ∝ T

V₀ ∝ ln [N_AN_D]

So built-in potential depends on both doping densities & temperature.

Explanation:

E₀ (eV) is defined as a shift in the energy band gap during the formation of the pn junction. The energy bandgap for a pn junction under thermal equilibrium is as shown:

At the p-side, the majority carrier holes is given by:

Since E₁ = E_pi – E_F, we can write:

Rearranging the above, we get:

Similarly, for the n-side, we can write:

The built-in potential is nothing but the deflection in the energy gap in total, i.e.

E₀ = E₁ + E₂

In terms of built-in voltage, we can write:

Memory Address Register

• The MAR is a special type of register that contains the memory address of the data and instruction.
• The main task of the MAR is to access instruction and data from memory in the execution phase

Additional Information

Index Register 

• The Index Register is the hardware element that holds the number.
• The number adds to the computer instruction's address to create an effective address.

​Program Counter

• Program Counter (PC) holds the address of the memory location of the next instruction, which is to be fetched after the current instruction is completed.

Concept:

The common base DC current gain is a ratio of the value of the transistor's collector current to the value of the transistor's emitter current, i.e.

   ---(1)

Also, the common-emitter current gain is the ratio of the value of the transistor's collector current to the value of the transistor's base current in a transistor, i.e.

   ---(2)

Using Equation (1) and (2), we get:

Calculation:

With β = 200, α will be:

α = 0.995

Concept:

Calculation:

Given:

B.W = 4000 Hz

α = 1

∴ B.W 

f_b = 4 kbps

To avoid inter symbol interference, the minimum bandwidth 

R_s is signalling rate

In 64-QAM 6-bits are sent together as a symbol

= 100 kHz

Let F(ω) is the Fourier transform of f(t).

• In fiber-optic communication, a diode laser is used for transmitting light signals into the fiber, and a photodiode is used for receiving the light signal.
• A photodiode is a device that converts a light signal to an electrical signal
• A photodiode is operated in the reverse-biased mode

Some important photodiodes are:

• PN photodiode
• PIN photodiode
• Avalanche photodiode

Notes:

PIN DIODE has three regions:

• P-type layer
• Intrinsic Layer
• N-Type layer
• The depletion region that exists between p and n regions is large. The layer between p and n regions includes no charge carriers
• In the reverse bias, as the depletion region of the diode has no charge carriers it works as an insulator
• The depletion region exists within the PIN diode but if the PIN diode is forward biased then carriers come into the depletion region and there will be a flow of current.

We know that,

Potential is given by

V = - 

dV = - E. dl cos θ 

|dV| = |E| |dl| cos θ 

if θ = 90° 

|dV| = |E| |dl| cos 90°  --------------------  (1)

|dV| = 0 -------------------    (2)

• Change in voltage zero i.e., voltage is constant.
• Surface with constant voltage is called equipotential surface.
• Actually ,meaning of (1) and (2) is when we move perpendicular to electric field voltage is constant. i.e, electric field and constant voltage surfaces are perpendicular.

In TCP/IP, presentation layer, session layer and application layer are merged into one application layer/ process layer. So, option 1 is correct.

Both the models are logical models and having similar architecture as both the models are constructed with the layers. So, option 2 is also correct

→ OSI is based on vertical approach

→ TCP/IP is based on horizontal approach

So, option 3 is incorrect

Given that 

Nyquist Rate 

Bit rate 

Bandwidth is ½ times of bit rate

Hence bandwidth is ½ (16) = 8 kHz

The Auto - correlation function is a measure of similarity between a signal and itself delayed by τ.

The function is given by,

F[x (t)] ↔ x(w)

F[x (t - τ)] ↔ e^-jwτ ×(w).

F[x × (t - τ)] ↔ e-jwτ x × (w).

By using parseval's identity for transform,

Inverse Fourier transform of square of sine function is always a triangular signal in time domain.

Concept:

Multiplication of two signals in the Time domain is actually the convolution in the frequency domain i.e. if we multiply two signals x₁(t) with x₂(t) in time domain, the frequency range of the resultant spectrum will from (-f₁ - f₂) to (f₁ + f₂). This is explained as shown:

Calculation:

Let

This has a frequency spectrum as shown:

Given  whose Fourier Transform is the convolution of the Individual Transforms.

The maximum frequency will then be 1 + 1 + 1 = 3 Hz

Now, Since x³(t) has a maximum frequency of 3Hz, the Nyquist frequency which is the minimum frequency to avoid aliasing = 2 f_max = 2 × 3 = 6Hz

• The overall power factor is defined as the cosine of the angle between the phase voltage and phase current. 
• In AC circuits, the power factor is also defined as the ratio of the real power flowing to the load to the apparent power in the circuit. 
• Hence power factor can be defined as watts to volt-amperes.

          Power factor = cos ϕ

          ϕ is the angle between the voltage and the current.

• For a purely resistive circuit, the angle between the voltage and current is 0°

          So power factor for a purely resistive circuit is:

          P.F. = cos 0° 

          P.F. = 1 (unity)

Important Point

• In a purely inductive circuit, the current lags the voltage by 90° and the power factor is lagging.
• In a purely capacitive circuit, the current leads the voltage by 90° and the power factor is leading.

The correct answer is option 2): Series in the control circuit

Concept:

• The push button switch is usually used to turn on and off the control circuit.
• It is used in electrical automatic control circuits to manually send control signals to control contactors, relays, electromagnetic starters, etc. 
• It is connected in series with the motor control circuit

Additional Information

• The threaded neck inserts through a hole cut into a metal or plastic panel, with a matching nut to hold it in place.
• Thus, the button faces the human operator(s) while the switch contacts reside on the other side of the panel.
• When pressed, the downward motion of the actuator breaks the electrical bridge between the two NC contacts, forming a new bridge between the NO contacts.
• The common industrial push button shown below

​

Gas metal arc welding (GMAW) or Metal inert gas arc welding (MIG):

• In this process the arc is formed between a continuous, automatically fed, metallic consumable electrode and welding job in an atmosphere of inert gas, and hence this is called metal inert gas arc welding (MIG) process.

• The type of operation is generally used in GMAW is Semi automatic.

• MIG welding power sources control voltage; this is done by either voltage stepped switches, wind handles, or electronically.

• The amperage that the power source produces is controlled by the cross sectional area of the wire electrode and the wire speed, i.e. the higher the wire speed for each wire size, the higher the amperage the power source will produce.

• Argon is used in MIG welding as shielding gas.
• Argon is denser than air and settles over the joint to protect the molten pool from atmospheric gas contamination.
• In addition, argon is easy to ionize, so it handles a long arc at low voltages well.
• When the inert gas is replaced by carbon dioxide then it is called CO2 arc welding or metal active gas (MAG) arc welding.
• The common name for this process is gas metal arc welding (GMAW). 

Applying KCL at node A, we get:

i₁ = 2 A + 3.5 A

= 5.5 A

The composite FET (Two FET connected in parallel can be drawn as)

∵ Both FET are identical

Overall g_m = 2g_m

Now, 

∵ both are parallel

ASK System:

1. For ASK Transmitter on-off keying is used.

2. In Amplitude Shift Keying (ASK) binary 1 is represented with the presence of carrier and binary 0 is represented with the absence of the carrier.

1 : s₁(t) = A_c cos 2πf_ct

0 : s₂ (t) = 0

Hence,

ASK = [± 10 V, 0, ± 10 V, ± 10 V, ± 10 V, ± 10 V, 0, 0]

Important Point

FSK (Frequency Shift Keying):

In FSK (Frequency Shift Keying) binary 1 is represented with a high-frequency carrier signal and binary 0 is represented with a low-frequency carrier, i.e. In FSK, the carrier frequency is switched between 2 extremes.

For binary ‘1’ → S₁ (A) = Acos 2π f_Ht

For binary ‘0’ → S₂ (t) = A cos 2π f_Lt. The constellation diagram is as shown:

ASK(Amplitude Shift Keying):

In ASK (Amplitude shift keying) binary ‘1’ is represented with the presence of a carrier and binary ‘0’ is represented with the absence of a carrier:

For binary ‘1’ → S₁ (t) = Acos 2π f_ct

For binary ‘0’ → S₂ (t) = 0

The Constellation Diagram Representation is as shown:

where ‘I’ is the in-phase Component and ‘Q’ is the Quadrature phase.

PSK(Phase Shift Keying):

In PSK (phase shift keying) binary 1 is represented with a carrier signal and binary O is represented with 180° phase shift of a carrier

For binary ‘1’ → S₁ (A) = Acos 2π f_ct

For binary ‘0’ → S₂ (t) = A cos (2πf_ct + 180°) = - A cos 2π f_ct

The Constellation Diagram Representation is as shown:

LAN Topology contains Bus, star, and rings.

Key Points

A star topology is a topology for a Local Area Network (LAN) in which all nodes are individually connected to a central connection point, like a hub or a switch.

In networking a bus is the central cable i.e. the main wire that connects all devices on a local area network (LAN).

A ring topology is a topology for a Local Area Network (LAN) in which every device has exactly two ​neighbors for communication purposes.

The correct answer is CPU cycle.

• The time required for the fetching and execution of one simple machine instruction is CPU cycle time.
• The fundamental sequence of steps that a CPU performs is called CPU Cycle, it is also known as the "fetch-execute cycle,".
• In simpler CPUs, the instruction cycle is executed sequentially, each instruction being processed before the next one is started.
• In most modern CPUs, the instruction cycles are instead executed concurrently, and often in parallel, through an instruction pipeline
• A clock cycle, or simply a "cycle," is a single electronic pulse of a CPU.
• During each cycle, a CPU can perform a basic operation such as fetching an instruction, accessing memory, or writing data.

Additional Information

• ​Real-time is a level of computer responsiveness that a user senses as sufficiently immediate or that enables the computer to keep up with some external process.
• Seek time is the time which is required by the drive to pick the read/write head and take it to the proper track of the disk.
  • The seek time is a part of the access time where the latter also includes latency time and overhead time.
• Delay time is the time required for a digital signal to travel from the input(s) of a logic gate to the output.

In the question, We have to find the common to all three figures which is shown below-

Here, The highlighted area is common to all shapes.

Hence, Option (3) is correct.

From Statement 1:

We have, D moved a distance of 40m towards north.

From there he turns to the right and walked for 30m and reached school.

Here, we can’t determine in which direction is D’s home from the school.

From Statement 2:

We have, D is facing south. He turns right and walk for 100m.

After that he turned to the left walk for 50m and reach home.

Here, we can’t determine in which direction is D’s home from the school.

Hence option B is correct.

United Nations Day is observed on October 24th each year to commemorate the organization's founding and promote its goals and achievements.

In the 2024 Council of Ministers, there are 30 Cabinet Ministers, 5 Ministers of State (Independent Charge) and 36 Ministers of State.

The information and communication (ICT) services sector includes information technology activities like software development; telecommunications activities; publishing activities, including software publication; motion picture and sound recording activities; radio and TV broadcasting and programming; and other information service activities.