MPPGCL JE Electronics Mock Test - 7 Free Online Test 2026

Digital to Analog Modulation technique is as shown.

Important Points

1) As shown, QAM is a mixture of both ASK and PSK.

2) QAM uses two carrier signals with the same frequency but with which are in quadrature. Quadrature here means out phase by 90°.

3) Since the two signals have the same frequency, they are detected using synchronous detection.

4) Hence, amplitude and the phase of the carrier frequency both vary with the message signal.

A constellation diagram of a QAM signal with 2 different amplitude levels and 8 different phases is shown:

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:

Vestigial Sideband Modulation is a type of amplitude modulation where a part of the signal called vestige is modulated, along with one sideband. The spectrum requirement is between DSB-SC and SSB (less than DSB-SC and more than SSB)

Vestigial Sideband Modulation (VSB) is used for video modulation in TV transmission due to the following reasons:

1) A workable compromise between the spectrum-conserving characteristics of single-sideband modulation and the demodulation simplicity of double-sideband amplitude modulation is found in the vestigial-sideband modulation.

2) Video signal exhibits a large bandwidth and significant low-frequency content which suggests the use of VSB.  

The spectrum of a vestigial sideband is as shown:

Important Point

In TV Transmission, FM is used for Audio transmission and AM for Video transmission.

Concept:

We know that:

• AND gate output is '0' (If any input is '0').
• AND gate output is '1' (If all inputs are '1').
• OR gate output is '1' (If any input is '1').
• OR gate output is '0' (If all inputs are '0').

Analysis:

In the given logic circuit:

Inputs: A, B, C, D

Output: x, y, z

Let us assume , name of AND gates are A₁,  A₂,  A₃

Solution:

Output of A₁ = 

Output of A₂ =

Output of A3 =

Output x =Output of A₁ +Output of A₂ 

Output y =Output of A2 +Output of A3 

Output z =Output of A3

 = A.B.C.D

Concept:

The general expression for a frequency modulated wave is given by:

SPM(t) = A_c [cosω_ct + k_pm(t)]

The instantaneous phase is given by:

Phase deviation is defined as:

Phase deviation = [Max [k_p m(t)]]

Instantaneous frequency is given by:

From the above, the frequency deviation will be:

Frequency deviation maximum

Calculation:

k_p = 2 rad/volts

Concept:

Calculation:

Given:

B.W = 4000 Hz

α = 1

∴ B.W 

f_b = 4 kbps

ASK, PSK and FSK are signaling schemes used to transmit binary sequences through free space. In these schemes, bit-by-bit transmission through free space occurs.

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:

Important Point

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:

Concept:

• By shortening the length of the p-region the reverse recovery time (t_n) is reduced considerably.
• The stored charges can be reduced by adding gold dopants, thereby reducing storage time (t_s).
• Hence, gold dopants are also called lifetime killer.

Generally, T = T_n = t_s + t_t (t_s → storage time, t_t → transition time)

Also, frequency 

Hence, on reducing the storage time and reverse recovery time, the frequency is increased, thereby increasing the switching speed of the diode.

Concept:

We know,

where,

R = Resistance

ρ = Resistivity of conductor

L = Length of conductor

A = Cross-sectional area of the conductor.

So, Resistance ∝ Resistivity

Calculation:

Given, Resistance of gold = 0.8 Ω

And Resistivity of measuring wire = 25 × gold resistivity

∴ Resistance of wire = 25 × gold resistance

= 25 × 0.8 Ω

= 20 Ω

Given that 

Nyquist Rate 

Bit rate 

Bandwidth is ½ times of bit rate

Hence bandwidth is ½ (16) = 8 kHz

Concept:

Shifting property of convolution

Convolution of the signal x(t) with the impulse gives the same signal as a result after the convolution.

x(t) ∗ δ(t) = x(t)

x(t) ∗ δ(t – t₀) = x(t – t₀)

Substitute ‘t – t₀’ in the place of ‘t’

calculation:

Given:

x(n) = {1, 1, 1, 1, 0.5, 0.5}

y(n) = conv (δ(n – 1), x(n)) 

Using property of impilse function:

y(n) = x(n - 1)

Important Point

Properties of δ(t):

1. 

2. 

3. x(t) δ(t – t₀) = x(t₀) δ(t – t₀)

4. 

5. 

6. 

Properties of δ(n):

1. x[n] δ[n] = x[0] δ[n]

2. 

3. x[n] δ[n – n₀] = x[n₀] δ[n – n₀]

4. 

5. δ[an] = δ[n]

Relation between I_CEO and I_CBO:

I_E = I_B + I_C

I_C = I_C (majority) + I_C (minority)

= αI_E­ + I_CBO

= α (I_B + I_C) + I_CBO

⇒ I_C (1 – α) = αI_B + I_CBO

For I_B = 0, I_C = I_CEO

⇒ I_CEO (1 – α) = I_CBO

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). 

Concept:

The total transmitted power for an AM system is given by:

Pc = Carrier Power

μ = Modulation Index

Calculation:

With PC = 400 W and μ = 0.75, the total power in the modulated wave will be:

P_t = 512.5 W

Note: The transmitted power is independent of the modulation index in the case of FM and PM.

Concept:

For M-array PSK or M-array QAM the bit-rate(R_b) is given as:

Bit-rate (R_b) is directly proportional to log₂M.

Analysis:

FSK is used for slow speed Modem so bit rate of FSK is too low

for 4 - DPSK modem: M = 4

for 8 - DPSK modem: M = 8

for 16 QAM modem: M = 16

The correct sequence of Bit-rate is given as:

FSK < 4-DPSK < 8-DPSK < 16-QAM

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

Concept:

• Antivirus software, also known as anti-malware, is a computer program used to prevent, detect, and remove malware.
• Examples of common antivirus programs include MacAfee, Norton Antivirus, Kaspersky Anti-Virus, and Zone Alarm Antivirus.

Important Points

• Cipher: It is a method of writing in which a secret pattern of a particular set of letters or symbols is used to represent other letters, symbols, etc.
• Adware: It is also called advertising-supported software by its developers, is software that generates revenue for its developer by automatically generating online advertisements on users’ screen or installation process
• Firewall: It is a network security system that monitors and controls the incoming and outgoing network traffic based on predefined security rules

The correct answer is 0.

Stack-based CPU organization uses zero address instruction.

Key Points

• The computers which use Stack-based CPU Organization are based on a data structure called a stack. 
• It makes use of the Last In First Out (LIFO) access technique, which is the most common in most CPUs.
• The address of the highest member of the stack, known as the Stack pointer, is stored in a register (SP).
• Push and Pop are the two most common operations done on the stack's operators. These two operations are only carried out from one end.
• This instruction contains the opcode only with no address field. It pops the two top data from the stack, subtracting the data, and pushing the result into the stack at the top. 
• PDP-11, Intel’s 8085, and HP 3000 are some examples of stack-organized computers. 

The advantages of Stack-based CPU organization – 

1. Efficient computation of complex arithmetic expressions. 
2. Execution of instructions is fast because operand data are stored in consecutive memory locations. 
3. The length of instruction is short as they do not have an address field. 

The disadvantages of Stack-based CPU organization –

• The size of the program increases. 

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.

Four friends W, X, Y and Z are students of Class 10th.

i) W and X are good in Hindi but poor in English.

ii) W and Y are good in Science but poor in Mathematics.

iii) Y and Z are good in English but poor in Social Studies.

iv) Z and X are good in Mathematics as well as in Science.

Thus we can see Y and Z pairs of friends are good, both in English and Science

Hence, the correct answer is "Y and Z".

One word substitution is Oligarchy.

Monarchy: A form of government with a monarch at the head.

Oligarchy: A small group of people having control of a country or organization.

Plutocracy: A state or society governed by the wealthy.

Autocracy: A system of government by one person with absolute power.

Insinuate means suggest or hint (something bad) in an indirect and unpleasant way
Some insinuate that he doesn't love India enough to defend it wholeheartedly
It's degrading for people like Romney to insinuate that they don't contribute

• Meaning of Fake: Not genuine, imitation or counterfeit.
• Meaning of Original: present or existing from the beginning; first or earliest
• Meaning of Trustworthy: able to be relied on as honest or truthful
• Meaning of Loyal: giving or showing firm and constant support or allegiance to a person or institution

The idea is to express that it is the first time that Oxford has allowed public to vote. Thus, only ‘history’ is the best fit while ‘course’ and ‘age’ are incorrect.

Hence, the correct answer is option D.

Checking Statement I:

Since there is no data given about Player and Champion, therefore, No player is Champion can not be derived.

Clearly, Statement I alone is not sufficient to answer the question.

Checking Statement II:

Statement II is the converse statement of the required conclusion.

Clearly, Statement II alone is sufficient to answer the question.

Hence, Option B is correct.

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

1st term = 1² = 1
2nd term = 2² = 4
3rd term = 3² = 9
4th term = 4² = 16
5th term = 5² = 25
Thus, Missing number = 6² = 36

The word Vanity (Noun) means : too much pride in your own appearance, abilities or achievements; arrogance.
The word Humility (Noun) means: the quality of being humble. 

The original sentence "Darjeeling grows tea" is in the active voice.

The correct option that expresses the same sentence in the passive voice is:

D. Tea is grown in Darjeeling.