PCB Design Practice Test — Questions and Answers

Question 1: Which of the following is a key aspect of expressions in the sum-of-products form?

The delay times are greatly reduced over other forms
All logic circuits are reduced to nothing more than simple AND and OR operations (Correct answer)
The maximum number of gates that any signal must pass through is reduced by a factor of two
No signal must pass through more than two gates, not including inverters

Correct answer: All logic circuits are reduced to nothing more than simple AND and OR operations

The sum-of-products (SOP) form in Boolean algebra expresses a logic function as a sum (OR) of product (AND) terms. Each product term consists of variables or their complements logically ANDed together. A key aspect is that any Boolean function can be realized using only AND and OR operations, making it a fundamental and easily implementable form for logic circuits.

Question 2: You have a part that isn't up to par with the blueprint. Who is in charge of resolving the situation?

Quality Assurance Manager
Material Planner
Product Engineer (Correct answer)
Supervisor

Correct answer: Product Engineer

A Product Engineer is typically responsible for the technical aspects of a product throughout its lifecycle, including design, development, and manufacturing support. If a part does not meet blueprint specifications, the Product Engineer is tasked with investigating the discrepancy, determining the root cause (e.g., design flaw, manufacturing error), and implementing corrective actions to ensure the product meets quality standards.

Question 3: What is the M16's standard ammo load?

100 Rounds
210 Rounds (Correct answer)
190 Rounds
140 Rounds

Correct answer: 210 Rounds

The standard ammo load for an M16 rifle in military contexts typically consists of seven 30-round magazines. This totals 210 rounds (7 magazines x 30 rounds/magazine). This loadout is designed to provide a balance between sufficient ammunition for combat engagements and the practical carrying capacity for an infantry soldier.

Question 4: How many times should a weapon be subjected to quick action?

1 (Correct answer)
4
5
3

Correct answer: 1

Quick action (or immediate action) is a rapid procedure performed to clear a stoppage in a firearm. It should generally be attempted only once. If the weapon does not fire after a single quick action, it indicates a more significant malfunction that requires a more thorough remedial action, involving a detailed inspection and clearing process, rather than repeated quick attempts.

Question 5: What are the sight picture's two essential elements?

Proper position, breathing
sight alignment, placing of the aiming point (Correct answer)
steady aim, proper position
breathing, firing

Correct answer: sight alignment, placing of the aiming point

The sight picture is critical for accurate shooting and comprises two essential elements: sight alignment and placing of the aiming point. Sight alignment involves correctly aligning the front sight with the rear sight. Placing of the aiming point then positions these aligned sights precisely onto the desired target area. Both must be correct for the shot to hit its intended mark.

Question 6: For the M16, what is the greatest effective range for a point target?

1100 Meters
1200 meter
400 meters
550 Meter (Correct answer)

Correct answer: 550 Meter

For the M16 rifle, the greatest effective range for a point target (a specific, small target like a human silhouette) is generally considered to be 550 meters. This distance represents the maximum range at which a trained shooter can consistently hit such a target with reasonable accuracy under optimal conditions. Beyond this range, the probability of hitting a point target significantly decreases.

Question 7: What is the Voltage Peak to Peak? According to the oscilloscope, Vpeak reads VA1= 10v and time reads T2-T1 = 10 ms.

50v
20v (Correct answer)
10v
40v

Correct answer: 20v

Vpeak (VA1) is the voltage from the center (0V) to the highest point of a waveform. Voltage Peak-to-Peak (Vpp) is the total voltage difference between the maximum positive peak and the maximum negative peak. For a symmetrical waveform, Vpp is always twice the Vpeak value. Given Vpeak = 10V, Vpp = 2 * 10V = 20V.

Question 8: What is the word that is being used to describe this? "the number of times the waveform repeats itself in one second"

Frequency (Correct answer)
Period
Amplitude
None of the above

Correct answer: Frequency

Frequency is a fundamental characteristic of a periodic waveform, defined as the number of cycles or repetitions that occur in one second. It is measured in Hertz (Hz), where one Hertz corresponds to one cycle per second. This definition directly matches the concept of how often a waveform repeats itself within a given timeframe.

Question 9: Which of the following is a form of electrical energy that may be converted by an electric circuit?

Heat and Magnetism (Correct answer)
Sound and Conductor
Conductor and Insulator
Magnetism and Lightning

Correct answer: Heat and Magnetism

Electric circuits are capable of converting electrical energy into various other forms. When current flows through a conductor, it generates heat due to resistance, a phenomenon known as Joule heating. Additionally, moving electric charges create magnetic fields, demonstrating the conversion of electrical energy into magnetism. These are common and fundamental energy transformations in electrical circuits.

Question 10: Consider doubling the voltage and halving the resistance in a basic dc circuit. The current state of affairs will

stay the same as it was before
become half as great
become four times as great (Correct answer)
become twice as great

Correct answer: become four times as great

According to Ohm's Law, Current (I) = Voltage (V) / Resistance (R). If the voltage is doubled (2V) and the resistance is halved (R/2), the new current becomes I' = (2V) / (R/2). This simplifies to I' = 4 * (V/R), meaning the current will become four times its original value.

Question 11: Which of the following will happen if one of the ornament bulbs in a string of bulbs is shorted out?

The current in the string will go up (Correct answer)
All the other bulbs will go out
The current in the string will stay the same
The current in the string will go down

Correct answer: The current in the string will go up

When a bulb in a series string is shorted out, its resistance effectively drops to near zero. This significantly reduces the total resistance of the entire series circuit. According to Ohm's Law (I = V/R), if the total resistance decreases while the supply voltage remains constant, the total current flowing through the string will increase.

Question 12: Consider three parallel resistors with values of 22 Ω, 27 Ω, and 33 Ω. What is the current drawn from a 12-volt battery when linked across this combination?

1.5 A
1.4 A (Correct answer)
15 mA
150 mA

Correct answer: 1.4 A

For parallel resistors, the equivalent resistance (Req) is calculated using the formula 1/Req = 1/R1 + 1/R2 + 1/R3. Plugging in the values, 1/Req = 1/22 + 1/27 + 1/33 ≈ 0.04545 + 0.03704 + 0.03030 = 0.11279, so Req ≈ 8.866 Ω. Using Ohm's Law, Current (I) = Voltage (V) / Req = 12V / 8.866Ω ≈ 1.35 A, which rounds to 1.4 A.

Question 13: The resistance of a coil is 30 and the inductance is 0.5H. If the coil's current is 4 amps and the frequency is 50 Hz, then What is the inductive reactance going to be?

157Ohms (Correct answer)
357Ohms
457Ohms
257Ohms

Correct answer: 157Ohms

Inductive reactance (XL) is the opposition of an inductor to alternating current and is calculated using the formula XL = 2 * π * f * L. Given a frequency (f) of 50 Hz and an inductance (L) of 0.5 H, XL = 2 * π * 50 Hz * 0.5 H. This calculation yields approximately 157.08 Ohms, which rounds to 157 Ohms. The coil's resistance and current are irrelevant for calculating inductive reactance alone.

Question 14: What is the M16's maximum effective range?

4300 meter
3500 meters
3400 meters
3600 meters (Correct answer)

Correct answer: 3600 meters

The M16 rifle's maximum range, which refers to the furthest distance its projectile can travel, is approximately 3600 meters. While its effective range for accurate target engagement is much shorter (typically 550-800 meters), the question asks for the 'maximum effective range,' which in some contexts can be interpreted as the maximum ballistic travel distance of the projectile.

Question 15: A series-parallel resistive network is frequently required by good engineering practice.

from a series combination of resistors in parallel but not from a parallel combination of resistors in series
from resistors that are all different
from a parallel combination of resistors in series, but not from a series combination of resistors in parallel
from resistors that are all identical (Correct answer)

Correct answer: from resistors that are all identical

While series-parallel networks often use various resistor values, in certain engineering practices, using identical resistors can be advantageous. This approach can simplify component sourcing, reduce manufacturing costs, and improve thermal tracking or matching characteristics, especially in applications requiring precision or symmetry, such as current mirrors or differential amplifiers.

Question 16: Which PCB name describes a thin photo-sensitive polymer that supports a photographic pattern of single traces or IC pads for etching?

Photo-resist (Correct answer)
Prepreg
Solder mask
Etching

Correct answer: Photo-resist

Photo-resist is a light-sensitive polymer material applied to a PCB substrate during the manufacturing process. It is selectively exposed to UV light through a photomask, which hardens the exposed areas. The unhardened areas are then washed away, leaving a protective pattern that defines the traces and pads before the etching process removes unwanted copper.

Question 17: Which type of solderability testing is performed when a solder sample is generated by immersing a wire or sheet metal specimen in molten solder?

Solder Iron Testing
Solder Bath Testing
Meniscus Rise Testing (Correct answer)
None of the above

Correct answer: Meniscus Rise Testing

Meniscus Rise Testing is a specific method used to evaluate the solderability of components or surfaces. It involves immersing a specimen, such as a wire or sheet metal, into a bath of molten solder. The height to which the solder rises along the specimen due to wetting forces (the meniscus) is then measured, with a higher rise indicating better solderability.

Question 18: Which of the following packages does not fall under the 'Small Outline Package' category?

SOP
SON (Correct answer)
SO
SOT

Correct answer: SON

SOP (Small Outline Package), SO (Small Outline, often referring to SOIC), and SOT (Small Outline Transistor) are all traditional small surface-mount packages characterized by having leads extending from the package body. SON (Small Outline No-lead) is a distinct package type that lacks external leads, instead using pads on the bottom of the package for electrical connection, thus not falling under the 'Small Outline Package' category in the same way.

Question 19: Which of the following methods falls under the heading of In-circuit Testing?

Component Testing
Apply Signal and check output
Impedance Testing
All of the above (Correct answer)

Correct answer: All of the above

In-circuit testing (ICT) is a comprehensive method for verifying the functionality and integrity of a populated printed circuit board. It encompasses various techniques, including checking individual component values (Component Testing), identifying shorts and opens (Impedance Testing), and applying signals to specific circuit sections to confirm their output (Apply Signal and check output). Therefore, all listed methods are integral parts of ICT.

Question 20: According to the supply lines for ________, high current circuits are purposefully situated or placed near the border of the PCB.

Reduction of path length
Removal of heat (Correct answer)
Isolation of stray current
All of the above

Correct answer: Removal of heat

High current circuits generate significant heat due to power dissipation (I²R losses). Placing these circuits and their associated supply lines near the border of the PCB facilitates more effective heat dissipation. This strategic placement allows for easier connection to external heat sinks or provides a better path for heat to radiate away from the board, preventing localized hot spots and improving overall reliability.

Question 21: Which of the soldering processes listed below is also known as 'High Frequency Resistance Soldering'?

Furnace Soldering
Electrical Soldering (Correct answer)
Iron Soldering
Torch Soldering

Correct answer: Electrical Soldering

Electrical soldering, particularly resistance soldering, can utilize high-frequency alternating current to generate heat directly at the joint through resistive heating. This method is highly efficient for precise, localized heating and joining of small components, making it synonymous with high-frequency resistance soldering in many industrial and specialized applications.

Question 22: Which of the following assumptions is not a grounding consideration for ADC and DAC?

Digital side to digital ground
Use of separate power supply and connection of their ground leads to single point reference
Reduction of inductive loop area between power and return traces (Correct answer)
Analog side to analog ground

Correct answer: Reduction of inductive loop area between power and return traces

For ADCs and DACs, critical grounding considerations include separating analog and digital grounds, connecting them at a single point reference, and ensuring proper return paths for analog and digital signals to prevent noise coupling. While reducing inductive loop area is a general good practice for signal integrity and EMI, it is a broader PCB layout principle rather than a specific grounding assumption unique to the isolation requirements of ADC/DACs, which focus on preventing noise transfer between domains via ground paths.

Question 23: Which phenomenon is not mitigated by low-impedance circuit lines, such as those provided by power and return planes for shielding purposes?

Convection (Correct answer)
Crosstalk
Radiation
Noise

Correct answer: Convection

Low-impedance circuit lines, such as those provided by power and ground planes, are highly effective at mitigating electrical phenomena like crosstalk, radiation (EMI), and noise by providing stable references and low-inductance return paths. However, convection is a heat transfer mechanism involving the movement of fluids (like air) and is not directly mitigated by the electrical properties of circuit lines or planes.

Question 24: Which of the following devices/equipments should be used to eliminate ground and supply line noise when constructing TTL/CMOS / ECL PCBs?

Snubber circuits
Coupling capacitor
Decoupling capacitor (Correct answer)
None of the above

Correct answer: Decoupling capacitor

Decoupling capacitors are crucial components placed close to the power pins of integrated circuits (such as TTL, CMOS, and ECL) on a PCB. They act as local reservoirs of charge, providing instantaneous current to the IC during rapid switching events and shunting high-frequency noise on the power and ground lines to ground, thereby stabilizing the supply voltage and reducing noise.

Question 25: What is/are the need(s) for precision differential amplifiers to be guarded?

To reduce capacitance between signal conductors & ground
To increase leakage resistance
A & B (Correct answer)
None of the above

Correct answer: A & B

Guarding in precision differential amplifiers is a technique used to improve accuracy by surrounding sensitive signal conductors with a low-impedance trace driven by a voltage equal to the signal. This method effectively reduces parasitic capacitance between the signal conductors and ground, and simultaneously increases the effective leakage resistance by diverting leakage currents away from the high-impedance input, both of which are crucial for maintaining measurement precision.

PCB Design Practice Test

Which of the following is a key aspect of expressions in the sum-of-products form?