MPPGCL JE Electronics Mock Test - 1 Free Online Test 2026

CONCEPT:

• The skin effect is the tendency of an alternating electric current to become distributed within a conductor such that the current density is largest near the surface of the conductor and decreases with greater depths in the conductor.
• The electric current flows mainly at the skin of the conductor, between the outer surface and a level called the skin depth.
• Skin depth is defined as the reciprocal of attenuation constant i.e.,

• The attenuation constant is given by:

• For an ideal conductor with σ ≈ ∞,

CALCULATION:

Given α = 400 /m

Skin depth is defined as the reciprocal of attenuation constant i.e.,

Important Point

α is the attenuation constant given by:

ω = Operating frequency

μ = Permeability of the material

σ = Conductivity of the material

For a good conductor σ >> 1. The above expression for the attenuation constant can be approximated as:

∴ The attenuation constant becomes:

Thus, the skin depth becomes:

Note: The skin depth is inversely proportional to the square root of frequency.

Concept:

The Energy of a signal is given by:

E = ∫x²(t) dt

In the ‘frequency domain’, the Energy is given by:

Calculation:

Given signal:

.

Now, Since the Energy of sinc function is easier to calculate in the frequency domain.

The Fourier Transform of sinc (5t) is represented as:

i.e

Energy = 1/5

I/O Mapped I/O Interfacing:

A kind of interfacing in which we assign an 8-bit address value to the input/output devices which can be accessed using IN and OUT instruction is called I/O Mapped I/O Interfacing.

Memory-mapped I/O-

It uses the same address space to address both memory and I/O devices.

The memory and registers of the I/O devices are mapped to (associated with) address values.

So when an address is accessed by the CPU, it may refer to a portion of physical RAM, or it can instead refer to memory of the I/O device.

Important Points

Differences between Memory Mapped I/O and I/O Mapped I/O-

1) Shift registers are sequential circuits that are used for storage or for the transfer of binary data.

2) The shift register takes the data present on the input and "shifts" it to the output once every clock cycle.

3) Every shift in the register content to the right by one-bit position is equivalent to dividing the original number by two 

4) Every shift in the register content to the left by one-bit position is equivalent to multiplying the original number by two.

This is explained with the help of the following Example:

Example:

Let the original content of a 4-bit right shift register is 0100 which is 4 in decimal, i.e.

(0100)2 = (4)10

1). Shifting the content of the register to the left by two-bit position, the new content now becomes (10000)2, which is 16 in decimal, i.e.

(10000)2 = (16)10

Clearly, the original number is multiplied by 4.

2). Shifting the content of the register to the right by one-bit position, the new content now becomes (0010)2, which is 2 in decimal, i.e.

(0010)2 = (2)10

Clearly, the original number is divided by 2.

Concept:

For a BJT expression for collector current (I_c) is defined as-

I_C = β I_B + (1 + β) I_co

Where β = large signal current gain in CE mode of operation

I_C = collector current

I_co = collector current when emitter is open

I_B = Base current

α = large signal current gain in CB mode of operation

Relation between α and β:

Calculation:

Given data: α = 0.98

I_co = 6 μA

I_B = 100 μA

I_c = β I_B + (1 + β) I_co

I_c = 49 × 100 + (49 + 1) 6 μA

I_c = 5200 μA

[ ∵ 1 μA = 10-6 A

1 mA = 10-3 A

1 mA = 103 μA ]

I_c = 5.2 mA

Fourier series:

The Fourier series for the function f(x) in the interval α < x < α + 2π is given by

where

An even function is any function f such that f(-x) = f(x)

Example: cos x, sec x, x², x⁴, x⁶ …….., x^-2, x^-4 ……..

An odd function is any function f such that f(-x) = -f(x)

Example: sin x, tan x, cosec x, cot x, n, x³ ……., x^-1, x^-3 ……..

When f is an even periodic function of period 2L, then its Fourier series contains only cosine (include possibly, the constant term) terms.

When f is an odd periodic function of period 2L, then its Fourier series contains only sine terms.

• Based on the symmetry of the periodic signal given we can conclude the Fourier series coefficients and the type of harmonics that are present in the signal given.
• With the Fourier series, the non-sinusoidal periodic waveform can be converted into the sinusoidal wave.

The below table shows the type of Fourier coefficient terms corresponding to the symmetry.

Concept:

QPSK is a modulation scheme that allows one symbol to transfer two bits of data. There are four possible two-bit numbers (00, 01, 10, 11).

For bandpass transmission,

Bandwidth for M-ary PSK  

Given:

BW = 36 × 10⁶ Hz

Roll-off factor = 0.2

Calculation:

Bandwidth for QPSK  

2 × 36 × 10⁶ = 1.2 R_b

R_b = 72/1.2 Mbps 

= 60 Mbps

Important Point

Concept:

For an FM system, the frequency modulation is given as:

δ = A_m k_f

A_m = Maximum amplitude of the modulating signal

k_f = Frequency sensitivity of the FM modulator.

Note: We observe that the frequency deviation in independent of the frequency of the modulating signal.

Calculation:

For A_m = 2.4 V, δ = 4.8 kHz, i.e.

4.8k = k_f × 2.4

∴ For A_m = 7.2 V, the dideviation will be:

δ = k_f × 7.2

δ = 14.4 kHz

Important Point

Modulation Index (β) in FM is given by:

k_f = frequency sensitivity

A_m = modulating voltage

Explanation:

CAD/CAM

• CAD stands for Computer-Aided Design whereas CAM is the abbreviation for Computer-Aided Manufacturing.
• CAD/CAM applications are used to both design a product and programme manufacturing processes, specifically, CNC machining.
• CAD and CAM can be set up to create a direct link between the design and manufacture of a product. The drawing geometry is then used in the CAM program to generate instructions for the CNC machine tools employing stamping, cutting, burning, bending and other types of operations.

Hardware devices which are used in CAD/CAM application:

Cursor control devices:

• Absolute touchpad
• Thumbwheels
• Mouse
• Trackball
• Light pen
• Relative touchpad
• Displacement joystick
• Force joystick

Applying the superposition theorem

Replace I₁ by open circuit

(R₁ + R) is in parallel with R₂

From current division

Replace I₂ by open circuit

(R₂ + R) is in parallel with R₁

From current division

I₁ = I₂ = 1 A

Total current

Substituting the values

• The VCO center frequency ω₀ differs from the frequency ω_i of the input signal
• Therefore, first the VCO frequency has to be tuned to the input frequency by the loop
• This process is called frequency pull-in
• Then the VCO phase has to be adjusted according to the input phase
• This process is known as phase lock-in

Depletion Mode n-MOS transistors have an n channel and are built on a p-type silicon substrate, whereas p-MOS Depletion mode transistors are built on an n-type substrate.

A thin gate oxide is present between the source and the drain regions.

• In Depletion Mode, the channel is already established due to the implant, even when V_gs = 0 V.
• A negative voltage (V_td) must be applied between the gate and the source for n-MOS to remove the channel.
• Similarly, a positive voltage (V_td) between the Source and Drain is required to remove the channel for P-MOS Depletion mode.

Important Points

Entrancement Mode Transistor Action:

In enhancement mode MOSFET, to establish a channel, a minimum voltage level called the threshold voltage (V_t) must be applied between the Gate and the source.

• When V_gs > V_t and V_ds = 0, it operates in the cut-off region. Channel is formed but not no current flows between the drain and source.
• For V_gs > V_t , V_ds < V_gs < V_gs - V_t,  it operates in the linear region.
• When V_ds is increased, the drain side becomes more reverse-biased and the channel starts to pinch.
• For V_gs > V_t, V_ds > V_gs - V_t, it operates in the saturation region and if V_ds is increased more and more, the increased voltage gets dropped in the depletion region, loading to const current.

Concept:

Mason’s Gain Formula

• It is a technique used for finding the transfer function of a control system. A formula that determines the transfer function of a linear system by making use of the signal flow graph is known as Mason’s Gain Formula.
• It shows its significance in determining the relationship between input and output.

Suppose there are ‘N’ forward paths in a signal flow graph. The gain between the input and the output nodes of a signal flow graph is nothing but the transfer function of the system. It can be calculated by using Mason’s gain formula.

Mason’s gain formula is

Where,

C(s) is the output node

R(s) is the input node

T is the transfer function or gain between R(s) and C(s)

P_i is the i^th forward path gain

Δ = 1−(sum of all individual loop gains) + (sum of gain products of all possible two non-touching loops) − (sum of gain products of all possible three non-touching loops) + ........

Δ_i is obtained from Δ by removing the loops which are touching the i^th forward path.

Calculations:

The forward paths are as follows:

P₁ = 5

P₂ = 2 × 3 × 4 = 24

The loops are as follows:

L₁ = -2, L₂ = -3, L₃ = -4, L₄ = -5

The two non-touching loops are:

L₁L₃ = 8

There is no three non-touching loops

By Mason’s gain formula:-

Concept:

Adaptive Delta Modulation (ADM):

• This Modulation is the refined form of delta modulation.
• This method was introduced to solve the granular noise and slope overload error caused during Delta modulation.
• In DM the step size is constant and depends on a maximum slope but in ADM the step size is varied according to the slope of the message signal.

Key Points

• In Adaptive Delta Modulation, the step size of the staircase signal is not fixed and changes depending upon the input signal.
• Here first the difference between the present sample value and previous approximation is calculated.
• This error is quantized i.e. if the present sample is smaller than the previous approximation, quantized value is high or else it is low. (This is performed by the comparator)
• The output of the one-bit quantizer is given to the Logic step size control circuit where the step size is decided.

Key Points

• A number with base 2 is known as a Binary Number, and numbers with base 10 are known as Decimal Numbers in the Number System.
• The decimal numbers are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and so on.
• Binary numbers, on the other hand, are used in digital systems and are represented by just two digits – 0 and 1.

Binary to Decimal Conversion:

Given:

Given binary number = (11010011)2

Calculation:

(11010011)2 = (1 × 27 + 1 × 26 + 0 × 25 + 1 × 24 + 0 × 23 + 0 × 22 + 1 × 21 + 1 × 20)10

⇒ (128 + 64 + 16 + 2 + 1)10

⇒ (211)10

So, the decimal equivalent of the binary number (11010011)2 is (211)10.

∴ The number at the place of the question mark will be 211.

The electric field at a distance 'r' due to a point charge is given by:

r = distance from the point charge

â_r = unit direction vector

This is explained with the help of the following diagram:

As the distance from the point charge decreases the magnitude also decreases.

Important Points:

• The direction is radial: outward for +|Q| and inward for -|Q|
• Magnitude: Constant on any spherical shell
• Flux through any shell enclosing Q is the same: E_AA_A = E_BA_B

Concept:

The Karnaugh map uses the following rules for the simplification of expressions by grouping together adjacent cells containing ones.

• Groups must not include any cell containing a zero.
• Groups may be horizontal or vertical, but not diagonal.
• Groups must contain 1, 2, 4, 8, or in general 2ⁿ cells. That is if n = 1, a group will contain two 1's since 2¹ = 2, if n = 2, a group will contain four 1's since 2² = 4 and so on.
• Groups may overlap.
• Groups may wrap around the table. The leftmost cell in a row may be grouped with the rightmost cell and the top cell in a column may be grouped with the bottom cell.

Calculation:

Global System for Mobile communication (GSM), is a globally accepted standard for digital cellular

Communication.

GSM specification defines the functions and interface requirements.

The GSM system is divided into 3-major systems:

• The switching system (ss)
• The Base station system (BSS)
• The operation & support system (OSS)

Concept:

The total number of complex multiplies for an N-point FFT is given by:

Calculation:

Given N = 32

So, for a 32-point FFT, the total number of complex multiplies required will be:

 = 16 × 5 = 80

The correct answer is option 2.

Concept:

Minimum header size of IPv4 = 20-byte

The maximum header size of IPv4 = 60 bytes

The header length field in the IPv4 header is 4 bits.

Maximum possible value (1111) = 15.

Explanation:

The given data,  the first 8 bits is 0100 0010,
The First 4 bits represent version IPV4 (0100).
And another 4 bits represent header length ( bits decimal value x 4) which should range between 20 to 60 bytes. This means that these 4 bits must represent the decimal number between 5 and 15.

Which is 2 × 4 = 8 bytes which is not possible since the minimum header length for IPv4 is 20 bytes.

Here (0010=2)

Here are the last bits of decimal value=2.
Hence Receiver will reject the packet.

Hence the correct answer is The receiver rejects the packet.

Solution

Given,

V_x is the voltage across the 4Ω resistance.

so the current through resistance 4Ω is, i_x= 

using KVL in inner loop 1, we have

Therefore i₁ = 1.25A

Hence the correct option is option 4

1st term = 3 * 1 = 3
2nd term = 3 * 3 = 9
3rd term = 3 * 9 = 27
4th term = 3 * 27 = 81

Thus, Missing number is 5th term = 3 * 81 = 243

The correct answer is Sikar.

Key Points

• ​Sahibi river:
  • Place of Origin- Jitgarh and Manoharpur of Sikar district in Rajasthan.
  • Entry in Haryana- Kot Kasin Rewari.
  • Passes through districts- Rewari, Gurugram.
  • Tributaries – Sota, Barkania Nala, Indori Nala
  • Merging or ending - gets absorbed in the Najafgarh lake.

Additional Information

Some of the rivers are:

Hence, "Printer" is the correct answer.

Important PointsInput Device: A piece of equipment/hardware that helps us enter data into a computer is called an input device. For example keyboard, mouse, etc. 

1. Keyboard:

• A simple device comprising keys and each key denotes either an alphabet, number, or number commands which can be given to a computer for various actions to be performed
• It has a modified version of typewriter keys
• The keyboard is an essential input device and computers and laptops both use keyboards to give commands to the computer

2. Joy Stick:

• It is a device that comprises a stick that is attached at an angle to the base so that it can be moved and controlled
• Mostly used to control the movement in video games
• Apart from a computer system, a joystick is also used in the cockpit of an aeroplane, wheelchairs, cranes, trucks, etc. to operate them well

3. Scanner:

• This device can scan images or text and convert it into a digital signal
• When we place any piece of a document on a scanner, it converts it into a digital signal and displays it on the computer screen

Output Device: A piece of equipment/hardware that gives out the result of the entered input, once it is processed (i.e. converts data from machine language to a human-understandable language), is called an output device. For example printers, monitors, etc. 

Printer:

• A device that makes a copy of the pictorial or textual content, usually over a paper is called a printer
• For example, an author types the entire book on his/her computer and later gets a printout of it, which is in the form of paper and is later published
• Multiple types of printers are also available in the market, which can serve different purposes

Hence, Option D is correct.

⇒ (2/1000) × (5/10)

⇒ (10/10000)

⇒ (1/1000) = 0.001

∴ 0.002 x 0.5 = 0.001