Electronic Mechanic MCQ Quiz - Objective Question with Answer for Electronic Mechanic - Download Free PDF

Explanation:

The 8051 microcontroller accesses external memory primarily through indirect addressing using the Data Pointer (DPTR).

Here's why:

• DPTR (Data Pointer): The DPTR is a 16-bit register in the 8051 that holds the 16-bit address of the external memory location to be accessed.

• MOVX Instruction: The 8051 uses special instructions like MOVX (Move External) to read from or write to external data memory. For example, MOVX A, @DPTR moves data from the external memory location pointed to by DPTR into the accumulator.

• Indirect Addressing: This method is called indirect addressing because the instruction doesn't directly specify the memory address but rather uses the content of a register (DPTR) as the address.

While the 8051 also has direct, immediate, and register addressing modes, these are primarily for accessing internal memory (RAM, SFRs) or for immediate data operations, not for accessing external memory.

Therefore, the correct option is: By using indirect addressing through DPTR

The correct answer is option 4

Explanation:

When interfacing external RAM with the 8051 microcontroller, the 8051 needs to output address and data signals to the external memory.

The 8051 uses:

• Port 0: Multiplexed lower 8 bits of address (A0–A7) and data bus (D0–D7).
  (This is why an external latch is needed to demultiplex address & data.)

• Port 2: Outputs the higher 8 bits of address (A8–A15) directly.

Explanation:

The Accumulator Register in the 8051 Microcontroller

Definition: The accumulator register in the 8051 microcontroller is a special-purpose register used extensively in arithmetic, logical, and data transfer operations. It acts as an intermediary for computation and is integral to the functioning of the microcontroller. The accumulator is denoted by the symbol "A" and is widely used in instructions for performing operations such as addition, subtraction, logical comparisons, and data transfers.

Address of the Accumulator Register: The accumulator register in the 8051 microcontroller has a specific address within the Special Function Register (SFR) memory space. The correct address for the accumulator register is 0E0h. This hexadecimal address is reserved for the accumulator in the microcontroller's architecture.

Explanation of Correct Option:

Option 1: 0E0h

The accumulator register in the 8051 microcontroller is located at the address 0E0h. This address falls within the SFR memory space, which ranges from 80h to FFh in the 8051 architecture. The SFRs are a specific set of memory locations used to control and monitor the microcontroller's operations. The accumulator register, being a core part of the 8051's functionality, is assigned to the address 0E0h for direct access during computations and instructions.

The accumulator is involved in almost every arithmetic and logical operation performed by the microcontroller. For instance, when an addition operation is executed, one operand is typically stored in the accumulator, and the result is also stored there. This makes the accumulator a pivotal element in the microcontroller's operation.

The correct answer is option 3

Concept:

• 8051 is an 8-bit (data bus) microcontroller built with 40 pins DIP (dual inline package).
• 8051 has internal RAM (128 Bytes) and ROM (4K Bytes).
• Of the 128-byte internal RAM, only 16 bytes are a bit-addressable. The rest must be accessed in byte format.

• Additional Information

  The Block Diagram of an 8051 microcontroller is as shown:

  

  In an 8051 microcontroller,

• Internal RAM (data memory) - 128 bytes
• Internal memory (code memory) - 4 kB (ROM)
• Timer/counter - 2
• No. of interrupt - 5
• I/O pins - 32
• Serial port - 1

Explanation:

Power Added Efficiency of Power Amplifier

Definition: Power added efficiency (PAE) is a key performance metric for power amplifiers, particularly in RF and microwave engineering. It measures the efficiency with which the amplifier converts the DC power it consumes into useful RF output power, considering the input signal power as part of the calculation.

Formula:

PAE is calculated using the following formula:

PAE = [(P_out - P_in) ÷ P_DC] × 100

Where:

• P_out: Output power (RF power delivered by the amplifier).
• P_in: Input signal power (RF power fed into the amplifier).
• P_DC: DC power supplied to the amplifier.

Calculation:

Given data:

• DC Voltage (V_DC): 8 volts
• DC Current (I_DC): 5 amps
• AC Input Signal Power (P_in): 0 dBm
• Output Power (P_out): 30 dBm

Step 1: Convert dBm values to watts.

• P_in (in watts) = 10^((0 - 30)/10) = 10^(-3) = 0.001 watts
• P_out (in watts) = 10^((30 - 30)/10) = 10^(0) = 1 watt

Step 2: Calculate DC power (P_DC).

P_DC = V_DC × I_DC

P_DC = 8 × 5 = 40 watts

Step 3: Calculate Power Added Efficiency (PAE).

PAE = [(P_out - P_in) ÷ P_DC] × 100

Substitute the values:

PAE = [(1 - 0.001) ÷ 40] × 100

PAE = [0.999 ÷ 40] × 100

PAE ≈ 0.025 × 100

PAE ≈ 2.5%

Conclusion: The approximate power added efficiency of the given power amplifier is 2.5%, which corresponds to Option 2

Concept:

Relation between mode, median and mean is given by:

Mode = 3 × median – 2 × mean

Calculation:

Given:

Mode – median = 2

As we know

Mode = 3 × median – 2 × mean

Now, Mode = median + 2

⇒ (2 + median) = 3median – 2mean   

⇒ 2Median - 2Mean = 2

⇒ Median - Mean = 1

CONCEPT:

Coulomb's law in Electrostatics:

• Coulomb's law state’s that force of interaction between two stationary point charges is directly proportional to the product of the charges, and inversely proportional to the square of the distance between them and acts along the straight line joining the two charges.

Faraday's Laws of Electromagnetic Induction :

• Whenever the number of magnetic lines of force (magnetic flux) passing through a circuit/coil changes an emf is produced in the circuit called induced emf.

Pascal’s law:

• Pressure at each and every point in the closed fluid is same.

Charles law:

• If the pressure remaining constant, the volume of the given mass of a gas is directly proportional to its absolute temperature.
  i.e. V ∝ T

EXPLANATION:

• Coulomb’s law states that the mutual electric force between two charges q₁ and q₂ separated by r distance can be given by

Force (F) ∝ q1 × q2

\(F \propto \;\frac{1}{{{r^2}}}\)

\(F = K\frac{{{q_1} \times {q_2}}}{{{r^2}}}\)

Where K is a constant = 9 × 109 Nm2/C2

• If we want to calculate mutual electric forces between multiple charges we have to apply superposition principle along with coulomb’s law.

Here a = 2; d = 4

⇒ A40th term = a + 39d = 2 + 39 × 4 = 2 + 156 = 158

∴ Sum of 40 terms = \(\frac{n}{2}\left[ {a + A40th} \right]\)

⇒ \(Sum = \frac{{40}}{2} \times \left[ {2 + 158} \right] = 20 \times 160 = 3200\)

∴ Sum of 40 terms = 3200

CONCEPT:

• The rate of work done is called power.
• It is denoted by P. The SI unit of power is the watt (W).

Power (P) = W / t

W = work done

t = time

EXPLANATION:

Dimensions of force is \(ML{T^{ - 2}}\).

Energy or Work done = Force × Distance 

Dimensions of energy is \(M{L^2}{T^{ - 2}}\).

 The dimensions of power = (Dimension of work) / Time (t) = (\(M{L^2}{T^{ - 2}}\))/T =  \(M{L^2}{T^{ - 3}}\).

CONCEPT:

• Dispersion: The splitting of light into its component colors is called dispersion.
• Reflection: Reflection of Light is the process of sending back the light rays which fall on the surface of an object.
• Refraction: The bending of the light beam as it travels from one medium to another is known as the refraction of light.
• It takes place at the boundary between the two mediums.

EXPLANATION:

There various stages of phenomenon in the formation of a rainbow:

• The ray is first refracted at the air-droplet interface and dispersed into 7 colors.
• The dispersed rays are then totally internally reflected by the droplet-air interface.
• The dispersed rays then undergo refraction at the droplet-air interface and finally rainbow is formed.
• In this, we can see that that refraction and total internal reflection plays an important role in rainbow formation also the splitting of white light into seven colors is caused because of phenomena known as dispersion
• Thus all three phenomenon- refraction, reflection and dispersion are responsible for the formation of a rainbow in the sky. Hence option 4 is correct.

The Correct Answer is 'Cathode ray oscilloscope.'

• The waveform of a certain signal can be studied by a cathode ray oscilloscope.

Key Points

• The cathode ray oscilloscope is an electronic instrument used to obtain waveforms when the different input signals are given
  • It is also called an oscillograph
  • It is a graph plotting device that is used to measure different characteristics of signals.
  • When horizontal deflection plates and vertical deflection plates of CRO (Cathode Ray Oscilloscope) are connected to two sinusoidal voltages, the patterns that appear at the CRO screen are called the Lissajous pattern
  • The Lissajous pattern obtained in a CRO depends upon frequency, amplitude, and phase relationship
  • The patterns used to measure phase and frequency with a cathode ray oscilloscope are called the Lissajous pattern

Additional Information

• It is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum.
  • The basic function of a spectrometer is to take light in, break it into its spectral components, digitize the signal as a function of wavelength, and read it out and display it through a computer.
  • The mass spectrometer, NMR spectrometer, and the optical spectrometer are the three most common types of spectrometers found in research labs around the world.
  • The incident light from the light source can be transmitted, absorbed, or reflected through the sample.
• A p-n junction diode is a two-terminal device, which allows the electric current in only one direction while blocks the electric current in the opposite or reverse direction
  • The p-n junction, which is formed when the p-type and n-type semiconductors are joined, is called a p-n junction diode.
• A sonometer is an apparatus made of a hollow box having two holes.
  • A string is attached to it by which the transverse vibrations of strings can be studied.

Concept:

Load Power = 150 watts

Rating of battery used in UPS = 12 Volts, 150 Ah

The energy supplied by battery = Voltage x Ah

Energy supplied by battery = 12 × 150 = 1800 watt-hour

∴ A battery can supply energy of 1800 watt-hour

Backup time = (Energy supplied by the battery)/(Load Power)

Backup time \(=\frac{1800}{150}=12~h\)

Root of the equation of 2x² + 4x = 30

2x² + 4x – 30 = 0

Divided by 2

x² + 2x – 15 = 0

x² + 5x – 3x – 15 = 0

x (x + 5) – 3 (x + 5) = 0

(x + 5) (x – 3) = 0

Taking,

(x + 5) = 0

x = (-5)

Taking,

(x – 3) = 0

x = 3

So, the roots of the equation of 2x² + 4x = 30 are (-5) and 3.

Tip: To find the answer quickly we can put the values of the options directly in the equation and check whether the values satisfy the equation. 

MS WORD is an example of Application Software.

Key Points

Application Software - Application software is a program or group of programs designed for end-users. Examples of an application include a word processor, a spreadsheet, an accounting application, a web browser, an email client, a media player, a file viewer, simulators, a console game, or a photo editor.

Additional Information

1. System Software - System software is software designed to provide a platform for other software. Examples of system software include operating systems like macOS, GNU/Linux, Android and Microsoft Windows, computational science software, game engines, industrial automation, and software as a service application.

2. Operating Software - An Operating System (OS) is an interface between a computer user and computer hardware. An operating system is software that performs all the basic tasks like file management, memory management, process management, handling input and output, and controlling peripheral devices such as disk drives and printers. Five of the most common operating systems are Microsoft Windows, Apple macOS, Linux, Android, and Apple's iOS.

3. Translating Program - A translator is a programming language processor that converts a computer program from one language to another. It takes a program written in source code and converts it into machine code. It discovers and identifies the error during translation.

Thus, option 3 is the correct answer.

• The sensation of electric shock is caused by the flow of electric current through the human body to the earth.
• When a person comes in contact with electrically live objects like water heaters, washing machines electric iron, etc., the extent of damages caused by this current depends on its magnitude and duration.
• This kind of current is called the leakage current which comes in milli-amps.
• These leakage currents being very small in magnitude, hence undetected by the fuses/MCBs are the major cause for the fires due to electricity.
• Residual current operated circuit breakers provide maximum protection from electric shocks and fires caused due to earth leakage current and also prevents the waste of electrical energy.
• These residual current circuit breakers (RCCB) are popularly called as earth leakage circuit breakers (ELCB).