Question 1

Match the logic families in List I with their characteristic properties in List II: A) TTL, B) ECL, C) NMOS, D) CMOS ↔ (1) Maximum power consumption, (2) Highest packing density, (3) Least power consumption, (4) Saturated logic. Choose the correct m…

Accepted Answer

Introduction: Different digital logic families exhibit distinct electrical and structural characteristics that affect speed, power, and integration density. This matching question evaluates recognition of hallmark properties of TTL, ECL, NMOS, and CMOS technologies. Given Data / Assumptions: List I: TTL, ECL, NMOS, CMOS. List II characteristics: maximum power consumption, highest packing density (historical context), least power consumption, saturated logic. Concept / Approach: TTL (Transistor-Transistor Logic) employs saturated switching, hence 'saturated logic.' ECL (Emitter-Coupled Logic) avoids saturation, enabling very high speed at the cost of large static currents – it thus has 'maximum power consumption.' NMOS historically achieved higher packing density than bipolar families like TTL and ECL for the same era. CMOS (Complementary MOS) uses complementary transistors with near-zero static power (except leakage), giving it the 'least power consumption.' Step-by-Step Solution: Step 1: Map TTL → Saturated logic (A-4).Step 2: Map ECL → Maximum power consumption (B-1).Step 3: Map NMOS → Highest packing density (C-2) in the historical comparison set.Step 4: Map CMOS → Least power consumption (D-3). Verification / Alternative check: Standard digital electronics texts list TTL as saturated, ECL as fastest/high-power, CMOS as low-power, and NMOS as a dense MOS technology relative to bipolar families of its era. Why Other Options Are Wrong: Any mapping that assigns TTL to non-saturated or ECL to low power contradicts canonical properties; swapping NMOS/CMOS roles mixes density and power traits. Common Pitfalls: Assuming modern CMOS always out-densifies NMOS in every historical comparison (this item frames density relative to TTL/ECL era); confusing speed with power consumption. Final Answer: A-4, B-1, C-2, D-3

Question 2

Match the following in basic semiconductor physics and materials: (A) p-type semiconductor, (B) n-type semiconductor, (C) Intrinsic semiconductor, (D) Tungsten — with: (1) silicon, (2) holes are majority carriers, (3) electrons are majority carriers…

Accepted Answer

Introduction / Context: Semiconductor device fundamentals require recognizing material types and charge carriers. This matching problem connects common semiconductor categories and an example material to their defining properties. Understanding majority carriers and intrinsic vs extrinsic behavior is essential in electronics and solid-state physics. Given Data / Assumptions: A: p-type semiconductor B: n-type semiconductor C: Intrinsic semiconductor D: Tungsten List II options: (1) silicon, (2) holes are majority carriers, (3) electrons are majority carriers, (4) is a metal Concept / Approach: Intrinsic semiconductors are undoped (pure) materials whose electron and hole concentrations are equal. Extrinsic (doped) semiconductors are either p-type (acceptor-doped, holes dominate) or n-type (donor-doped, electrons dominate). Tungsten is a refractory metal used for filaments and contacts, not as a semiconductor. Step-by-Step Solution: Match A (p-type) → majority carriers are holes → 2.Match B (n-type) → majority carriers are electrons → 3.Match C (Intrinsic) → classic intrinsic example is pure silicon (or germanium) → choose 1 (silicon).Match D (Tungsten) → elemental metal with high melting point → 4 (is a metal). Verification / Alternative check: Check internal consistency: p-type corresponds to acceptor doping (e.g., boron in silicon) → holes dominate. n-type corresponds to donor doping (e.g., phosphorus/arsenic) → electrons dominate. Intrinsic silicon is the canonical teaching example. Tungsten's conduction band is partially filled → metallic behavior. Why Other Options Are Wrong: A-1, B-2, C-3, D-4: Swaps intrinsic with a material label and mis-assigns majority carriers. A-4, B-3, C-2, D-1: Calls p-type a metal and assigns silicon to tungsten. A-3, B-1, C-2, D-4: Reverses the majority carriers for p-/n-type and mislabels intrinsic. Common Pitfalls: Confusing intrinsic (pure) with n-type or p-type (doped). Assuming any elemental solid like tungsten can be a semiconductor—it is a metal. Final Answer: A-2, B-3, C-1, D-4

Question 3

Match camera pick-up technologies with their originators: (A) CCD (charge-coupled device), (B) Newvicon, (C) Plumbicon, (D) Chalnicon — with: (1) Toshiba, (2) Philips, (3) Matsushita (Panasonic), (4) RCA.

Accepted Answer

Introduction / Context: Video imaging history spans vacuum pick-up tubes and solid-state sensors. Recognizing who introduced key devices helps anchor technology timelines in broadcast engineering and electro-optics. Given Data / Assumptions: Devices: CCD, Newvicon, Plumbicon, Chalnicon. Developers to match: Toshiba, Philips, Matsushita (Panasonic), RCA. Concept / Approach: Associate each sensor with the company historically credited for its development or naming: Plumbicon is strongly associated with Philips; Newvicon with Matsushita; Chalnicon with Toshiba in common exam taxonomies; early CCD commercialization included notable work by RCA, even though CCD invention traces to Bell Labs. Step-by-Step Solution: Map Plumbicon → Philips → C-2.Map Newvicon → Matsushita (Panasonic) → B-3.Map Chalnicon → Toshiba → D-1 (common classification in broadcast exam literature).Map CCD (charge-coupled device) → RCA (commercial development lineage used in exam keys) → A-4. Verification / Alternative check: Cross-checking typical exam prep materials: Plumbicon ↔ Philips is consistent; Newvicon ↔ Matsushita is standard; Chalnicon frequently appears with Toshiba; CCD often paired with RCA in older broadcast syllabi despite Bell Labs' invention. Why Other Options Are Wrong: A-3, B-4, C-1, D-2: Swaps Newvicon and CCD and misplaces Plumbicon. A-4, B-3, C-1, D-2: Misassigns Plumbicon to Toshiba. A-1, B-2, C-3, D-4: Incorrectly pairs nearly all items. Common Pitfalls: Confusing invention site (Bell Labs for CCD) with later commercial associations used in test keys. Mixing up trade names (Plumbicon, Newvicon, Chalnicon) among Japanese and European manufacturers. Final Answer: A-4, B-3, C-2, D-1

Question 4

Match common DOS commands with their primary functions: (A) ATTRIB, (B) SCANDISK, (C) MOVE, (D) TREE — with: (1) displays all directories and subdirectories, (2) moves files to another directory, (3) checks the status of the disk, (4) hides or chang…

Accepted Answer

Introduction / Context: DOS utilities provide file, directory, and disk-maintenance operations. Knowing what each command does is essential for legacy systems and foundational operating-system literacy. Given Data / Assumptions: Commands: ATTRIB, SCANDISK, MOVE, TREE. Functions: list directory tree, move files, check disk status, set/hide attributes. Concept / Approach: Map each command to its main purpose from standard DOS help manuals: ATTRIB changes attributes; SCANDISK checks/repairs; MOVE relocates files; TREE displays directory hierarchy. Step-by-Step Solution: ATTRIB → attribute operations like +H (hidden), +R (read-only) → A-4.SCANDISK → surface/media and filesystem checks → B-3.MOVE → transfers files to another directory or drive → C-2.TREE → prints directory and subdirectory structure → D-1. Verification / Alternative check: Running 'command /?' or DOS manuals confirms each mapping (ATTRIB, SCANDISK, MOVE, TREE) with the listed functions. Why Other Options Are Wrong: A-1, B-2, C-3, D-4: Swaps TREE with ATTRIB and misassigns others. A-3, B-4, C-2, D-1: Interchanges ATTRIB and SCANDISK purposes. A-2, B-3, C-4, D-1: Mixes up ATTRIB and MOVE. Common Pitfalls: Assuming ATTRIB merely hides files; it can set multiple attributes (+R, +H, +S). Confusing SCANDISK with CHKDSK; both check disks, but SCANDISK (DOS 6.x) offered enhanced repair/reporting. Final Answer: A-4, B-3, C-2, D-1

Question 5

Match semiconductor elements and dopants to their properties: (A) Silicon, (B) Arsenic, (C) Indium, (D) Germanium — with: (1) is trivalent (acceptor), (2) rarely used as a semiconductor today, (3) is pentavalent (donor), (4) intrinsic semiconductor …

Accepted Answer

Introduction / Context: Doping changes the electrical behavior of semiconductors by introducing donors or acceptors. This question ties each listed element to its typical role or property in semiconductor technology. Given Data / Assumptions: Silicon (Si) and Germanium (Ge) are group-IV base semiconductors. Arsenic (As) is a group-V donor; Indium (In) is a group-III acceptor. Contemporary mainstream devices overwhelmingly use silicon; germanium is comparatively rare in bulk devices (though present in specialized heterostructures). Concept / Approach: Map periodic-table group to doping role: group-V → pentavalent donor (n-type); group-III → trivalent acceptor (p-type). Silicon is the canonical intrinsic substrate material in teaching contexts; germanium is much less common today in mass production. Step-by-Step Solution: A (Silicon) → intrinsic base material → 4.B (Arsenic) → pentavalent donor (n-type) → 3.C (Indium) → trivalent acceptor (p-type) → 1.D (Germanium) → comparatively rare as a modern semiconductor base → 2. Verification / Alternative check: Group mapping: Si/Ge are group 14; As is group 15 (donor); In is group 13 (acceptor). Historical usage shows a move from Ge to Si for thermal stability and oxide quality. Why Other Options Are Wrong: A-1, B-2, C-3, D-4: Mislabels silicon and germanium roles and swaps dopant valences. A-4, B-3, C-2, D-1: Puts Indium as 'rarely used as a semiconductor,' which is inaccurate for its dopant role. A-2, B-1, C-3, D-4: Reverses donor/acceptor assignments. Common Pitfalls: Confusing 'intrinsic' (pure material) with 'p-type' or 'n-type' (doped). Thinking germanium is equally common today; it is niche compared to silicon. Final Answer: A-4, B-3, C-1, D-2

Question 6

Match the dimensional formulas (in M-L-T-I notation) to quantities: (A) Resistance, (B) Inductance, (C) Capacitance, (D) Reluctance — with: (1) M^-1 L^-2 T^2 I^2, (2) M L^2 T^-2 I^-2, (3) M^-1 L^-2 T^4 I^2, (4) M L^2 T^-3 I^-2.

Accepted Answer

Introduction / Context: Dimensional analysis in electromagnetism relates electrical quantities to base dimensions M (mass), L (length), T (time), and I (current). Matching correct dimensions helps validate formulas and perform unit checks across problems. Given Data / Assumptions: A: Resistance (ohm = V/A). B: Inductance (henry = V*s/A). C: Capacitance (farad = C/V). D: Reluctance (magnetic) is analogous to 1/inductance in dimensional terms. Concept / Approach: Use base relations: V = W/Q = (J/s)/A = (M L^2 T^-3)/I; then compute each quantity by substitution and simplification. Step-by-Step Solution: Voltage dimension: V → M L^2 T^-3 I^-1.A (Resistance R) = V / I → M L^2 T^-3 I^-2 → match 4.B (Inductance L) = (V * s) / I → (M L^2 T^-3 I^-1 * T) / I = M L^2 T^-2 I^-2 → match 2.C (Capacitance C) = Q / V = (I * T) / (M L^2 T^-3 I^-1) = M^-1 L^-2 T^4 I^2 → match 3.D (Reluctance S) ≈ 1 / inductance → (M L^2 T^-2 I^-2)^-1 = M^-1 L^-2 T^2 I^2 → match 1. Verification / Alternative check: Cross-check using energy in inductor W = (1/2) L I^2 → L = 2W / I^2; since W has dimensions M L^2 T^-2, L → M L^2 T^-2 I^-2, consistent with above. Why Other Options Are Wrong: A-1, B-2, C-3, D-4: Assigns reluctance and resistance incorrectly. A-2, B-1, C-3, D-4: Misplaces resistance and inductance; reluctance not 4. A-2, B-4, C-3, D-1: Gives an impossible dimension (4) to inductance. Common Pitfalls: Forgetting that resistance involves T^-3 (from V) rather than T^-2. Confusing magnetic reluctance with electrical resistance; they are analogous but dimensionally inverse to inductance. Final Answer: A-4, B-2, C-3, D-1

Question 7

Match antennas to their typical directivity levels: (A) Horn antenna, (B) Parabolic antenna, (C) Lens antenna — with: (1) high directivity, (2) very high directivity, (3) moderate directivity.

Accepted Answer

Introduction / Context: Antenna directivity measures how concentrated the radiated power is in a particular direction. Recognizing typical directivity ranges for common microwave antennas is essential in RF system design. Given Data / Assumptions: Antennas: Horn, Parabolic reflector, Dielectric lens. Directivity labels: moderate, high, very high. Concept / Approach: A horn provides aperture matching and moderate gain; a parabolic reflector focuses energy tightly for very high directivity; a lens antenna increases directivity by phase-front shaping, generally between horn and large parabolic dishes. Step-by-Step Solution: Horn → moderate directivity (often tens of dBi when large, but typically below equivalent large dishes) → 3.Parabolic → very high directivity due to large effective aperture and precise focusing → 2.Lens → high directivity (improves collimation beyond horns without reflectors) → 1. Verification / Alternative check: Rule of thumb: Directivity ∝ effective aperture area. Parabolic reflectors typically achieve the highest for a given size; horns are simpler waveguide flares; lenses add focusing power without reflectors. Why Other Options Are Wrong: A-1, B-2, C-3: Overstates horn and understates lens relative positions. A-3, B-1, C-2: Swaps lens and parabolic levels. A-1, B-3, C-2: Misorders all three against typical practice. Common Pitfalls: Equating gain one-for-one with size without considering aperture efficiency. Assuming horns inherently provide very high directivity regardless of dimensions. Final Answer: A-3, B-2, C-1

Question 8

Match microwave measuring instruments with what they measure: (A) Bolometer, (B) VSWR meter, (C) Cavity wavemeter, (D) Pattern recorder — with: (1) reflection coefficients, (2) half-power beam widths, (3) microwave power, (4) microwave frequency.

Accepted Answer

Introduction / Context: Microwave labs rely on specialized meters to quantify power, frequency, impedance match, and antenna patterns. Matching each instrument to its primary measurement helps in selecting the right tool for diagnostics and design. Given Data / Assumptions: Bolometer → thermal power sensor. VSWR meter → standing wave ratio and reflection coefficient on lines. Cavity wavemeter → resonant frequency indicator. Pattern recorder → antenna radiation pattern characteristics. Concept / Approach: Identify the principal use of each instrument in a standard microwave bench setup. Step-by-Step Solution: Bolometer → measures absorbed microwave power via resistance change → 3.VSWR meter → relates voltage standing waves to reflection coefficient Γ → 1.Cavity wavemeter → mechanical tuning to resonance for frequency readout → 4.Pattern recorder → extracts beamwidths (including half-power points) from pattern sweeps → 2. Verification / Alternative check: On a reflex klystron setup, frequency is read from the cavity wavemeter dial, line match from VSWR, power by bolometer bridge, and antenna beamwidth from the recorded pattern. Why Other Options Are Wrong: A-2, B-1, C-4, D-3: Assigns antenna beamwidth to bolometer and swaps D. A-2, B-4, C-1, D-3: Misplaces three entries. A-3, B-4, C-1, D-2: Confuses VSWR and frequency functions. Common Pitfalls: Using a power meter to infer frequency—power devices do not provide frequency readout. Confusing VSWR (line measure) with free-space antenna pattern parameters. Final Answer: A-3, B-1, C-4, D-2

Question 9

Match Field-Effect Transistor (FET) parameters to typical order-of-magnitude values (corrected units): (A) gm for JFET, (B) rd for JFET, (C) rd for MOSFET, (D) gg for JFET — with: (1) 25 kΩ, (2) 0.01 S, (3) 0.5 MΩ, (4) 10^-8 S.

Accepted Answer

Introduction / Context: Designers often estimate FET small-signal parameters by order of magnitude. Typical room-temperature values help with quick checks before detailed datasheet review or SPICE extraction. The original options mixed units ambiguously (e.g., 'mW' for a conductance). Here, units are corrected for clarity. Given Data / Assumptions: gm (transconductance) is measured in siemens (S). rd (drain resistance) is measured in ohms (Ω). gg (gate conductance) is extremely small (near leakage), in siemens (S). Typical magnitudes: gm for JFET in the mS to 10 mS range; rd for JFET on the order of tens of kΩ; rd for MOSFET (small-signal, triode-region excluded) can be hundreds of kΩ to mega-ohms; gg for JFET around 10^-8 S (or lower). Concept / Approach: Map each parameter to a plausible magnitude used in hand calculations and conceptual exam problems. Step-by-Step Solution: A (gm for JFET) → choose 0.01 S (10 mS) as a representative exam value → 2.B (rd for JFET) → tens of kΩ typical → 25 kΩ → 1.C (rd for MOSFET) → often higher than JFET → pick 0.5 MΩ → 3.D (gg for JFET) → tiny leakage conductance → ~10^-8 S → 4. Verification / Alternative check: Sanity check: gm * rd for JFET gives intrinsic gain order gmrd ≈ (10 mS)(25 kΩ) ≈ 250, a reasonable small-signal estimate. MOSFET's higher rd aligns with channel-length modulation effects. Why Other Options Are Wrong: A-1, B-2, C-3, D-4: Assigns JFET gm to 25 kΩ (wrong unit and concept). A-4, B-2, C-3, D-1: Gives gm an unphysically tiny conductance and swaps resistances. A-2, B-3, C-1, D-4 (distractor): Misplaces which device typically has larger rd. Common Pitfalls: Confusing resistance (Ω) with conductance (S); they are reciprocals. Using power units (W) by mistake for small-signal parameters. Final Answer: A-2, B-1, C-3, D-4

Question 10

Match Pascal library functions to acceptable argument types or domains: (A) ROUND X, (B) ABS X, (C) SQR X, (D) SIN X — with: (1) X in radians, (2) X real, (3) X real or integer.

Accepted Answer

Introduction / Context: Classic Pascal provides standard functions with defined argument types. Knowing which functions accept integers, reals, or require angular input in radians is a common programming-language fundamentals topic. Given Data / Assumptions: ROUND(X) converts a real to the nearest integer. ABS(X) returns absolute value; works for integer and real overloads. SQR(X) returns the square; works for integer and real overloads. SIN(X) expects an angle in radians. Concept / Approach: Check each function's signature in standard Pascal (e.g., Turbo Pascal, ISO Pascal) and match to the most general argument category presented in the options. Step-by-Step Solution: A (ROUND X) → X must be real (fractional allowed) → 2.B (ABS X) → X can be integer or real (overloaded) → 3.C (SQR X) → valid for integer or real (overloaded) → 3.D (SIN X) → X is an angle in radians for trigonometric functions → 1. Verification / Alternative check: In many Pascal dialects: 'ROUND: real → integer; ABS: same type out; SQR: same type out; SIN: real in radians → real.' Example: SIN(pi/2) = 1.0 when X is in radians. Why Other Options Are Wrong: A-2, B-3, C-1, D-3: Assigns SQR to radians and makes SIN accept integer/real nonsensically. A-3, B-2, C-2, D-1: Claims ROUND accepts integer, which defeats its purpose. A-2, B-3, C-2, D-1: Narrows SQR to reals only; it also works for integers. Common Pitfalls: Feeding degrees into SIN without converting to radians. Expecting ROUND to accept integers (it is for rounding reals). Final Answer: A-2, B-3, C-3, D-1

Question 11

Match the items correctly: (A) SSB (Single-Sideband) modulation, (B) ∇ · B = 0, (C) Modal dispersion — with (1) Transmission line, (2) Hilbert transform, (3) Faraday’s law, (4) Absence of magnetic monopoles, (5) Waveguides, (6) Phase-locked loop.

Accepted Answer

Introduction: This matching problem connects three distinct concepts to their canonical associations in communications and electromagnetics: (A) SSB modulation in signal processing, (B) the divergence of magnetic flux density in Maxwell’s equations, and (C) modal dispersion in guided-wave structures. Correct matching relies on recognizing the theoretical tool or physical principle each item is best known for. Given Data / Assumptions: A: Single-Sideband (SSB) is a bandwidth-efficient modulation. B: ∇ · B = 0 expresses a fundamental Maxwell relation. C: Modal dispersion occurs in multi-mode guided media. Available matches: (1) Transmission line, (2) Hilbert transform, (3) Faraday’s law, (4) Absence of magnetic monopoles, (5) Waveguides, (6) Phase-locked loop. Concept / Approach: SSB generation and analysis commonly use the Hilbert transform to create a 90-degree phase-shifted quadrature (analytic) signal, enabling sideband suppression. The equation ∇ · B = 0 states that magnetic flux lines have no beginning or end, capturing the absence of magnetic monopoles. Modal dispersion is inherent to waveguides (including multimode fiber), where different modes propagate with distinct velocities, spreading pulses. Step-by-Step Solution: A (SSB) → Hilbert transform: analytic-signal methods yield single-sideband signals via quadrature components.B (∇ · B = 0) → Absence of magnetic monopoles: divergence-free B indicates there are no isolated magnetic charges.C (Modal dispersion) → Waveguides: multi-mode structures support different propagation constants, causing dispersion. Verification / Alternative check: Alternative SSB realizations (filter method, phasing method) still hinge on quadrature generation; the phasing method specifically uses the Hilbert transform. Maxwell’s equations universally support ∇ · B = 0. Modal dispersion is not a property of a simple two-conductor transmission line (single TEM mode), but of multi-mode guiding structures. Why Other Options Are Wrong: (1) Transmission line for SSB is too generic and not the key enabling tool. (3) Faraday’s law pertains to time-varying flux and induced EMF, not ∇ · B. (6) PLLs relate to carrier/clock recovery, not SSB synthesis per se. Common Pitfalls: Confusing general RF blocks (PLLs, mixers) with the specific mathematical construct used in SSB; mixing Maxwell relations (curl vs divergence) for B-fields. Final Answer: A-2, B-4, C-5

Question 12

Match the controllers to their roles: (A) DMA controller, (B) CRT (display) controller, (C) Interrupt controller — with (1) Interface between computer and video display adapter, (2) Used to read data directly from disk into main memory, (3) Supervis…

Accepted Answer

Introduction: This question checks fundamental computer-organization knowledge: differentiating between DMA, display, and interrupt controllers. Each controller solves a distinct bottleneck in data movement, display timing, or interrupt handling. Given Data / Assumptions: A: DMA controller — offloads block transfers between I/O and memory. B: CRT controller — legacy term for video/display adapter timing and interfacing. C: Interrupt controller — arbitrates and prioritizes interrupt signals to the CPU. Roles: (1) video interface, (2) direct memory access for disk-to-memory reads, (3) interrupt signalling supervision. Concept / Approach: DMA eliminates CPU involvement in byte/word transfers, improving throughput. The CRT (or display) controller generates necessary raster timing and interacts with the display adapter/framebuffer. The interrupt controller (e.g., PIC) collects, prioritizes, and signals interrupts to the processor, simplifying CPU external-interrupt handling. Step-by-Step Solution: Map A → (2): DMA reads/writes memory directly for high-speed I/O like disk.Map B → (1): CRT controller provides the interface/timing for the display adapter.Map C → (3): Interrupt controller supervises interrupt requests and prioritization. Verification / Alternative check: Classic PC architecture (e.g., 8237 DMA, 6845/CRT controllers, 8259 PIC) demonstrates these roles distinctly. Why Other Options Are Wrong: Swapping these roles conflates data movement (DMA), video timing (CRT), and event signalling (PIC), which are architecturally separate. Common Pitfalls: Assuming modern GPUs or APICs change fundamentals; despite evolution, DMA handles block transfers, display controllers handle timing, and PIC/APIC manage interrupts. Final Answer: A-2, B-1, C-3

Question 13

Match the Boolean-algebra laws to their relational forms: (A) Distributive law, (B) De Morgan’s law, (C) Idempotent law, (D) Involution law — with (1) x + x = x, (2) x(y + z) = xy + xz, (3) (x)̄̄ = x, (4) (x + y)̄ = x̄ ȳ.

Accepted Answer

Introduction: Boolean algebra laws provide the algebraic toolkit for simplifying logic expressions and designing digital circuits. This item tests recognition of four cornerstone identities and their canonical forms. Given Data / Assumptions: A: Distributive law. B: De Morgan’s law. C: Idempotent law. D: Involution (double-complement) law. Relational forms: (1) x + x = x, (2) x(y + z) = xy + xz, (3) (x)̄̄ = x, (4) (x + y)̄ = x̄ ȳ. Concept / Approach: Each law has a standard, widely used expression. The distributive law expands products over sums. De Morgan’s laws transform complements of sums/products. Idempotence states redundancy of combining a variable with itself. Involution states that complementing twice restores the original variable. Step-by-Step Solution: A → (2): x(y + z) = xy + xz (distribution of product over sum).B → (4): (x + y)̄ = x̄ ȳ (the dual is (xy)̄ = x̄ + ȳ).C → (1): x + x = x (and x·x = x).D → (3): (x)̄̄ = x (double negation). Verification / Alternative check: Truth tables or Venn diagrams confirm each identity; Karnaugh maps also illustrate idempotence and distributivity. Why Other Options Are Wrong: Any permutation that mismatches these canonical forms contradicts standard Boolean identities taught in digital logic. Common Pitfalls: Confusing De Morgan’s transformations or mixing the two De Morgan forms; forgetting that idempotence applies to both + and · operations. Final Answer: A-2, B-4, C-1, D-3

Question 14

Match Java operators to their meanings: (A) & , (B) ^ , (C) || , (D) && — with (1) Logical AND, (2) Bitwise AND, (3) XOR, (4) Logical OR.

Accepted Answer

Introduction: Java differentiates between bitwise and logical operators, and it provides distinct symbols for exclusive OR and short-circuit logical operations. Mapping each operator to its meaning reinforces correct usage in expressions and conditionals. Given Data / Assumptions: Operators: & , ^ , || , &&. Meanings: logical AND/OR, bitwise AND, XOR. Context: Java operator precedence and boolean vs integral contexts. Concept / Approach: The single-ampersand & is bitwise AND for integer types (and a non-short-circuit boolean AND). The caret ^ is bitwise XOR (boolean XOR for booleans). The double-vertical-bar || is logical OR with short-circuit evaluation. The double-ampersand && is logical AND with short-circuit evaluation. Step-by-Step Solution: Map & → Bitwise AND (2).Map ^ → XOR (3).Map || → Logical OR (4).Map && → Logical AND (1). Verification / Alternative check: Code trials show that || and && may skip the right-hand operand when left-hand decides the outcome, while & and ^ always evaluate both sides for booleans and operate bitwise on integers. Why Other Options Are Wrong: Swapping logical and bitwise semantics leads to subtle bugs, particularly from assuming & is short-circuiting. Common Pitfalls: Using & instead of && in conditionals (causes unintended evaluation); misunderstanding ^ as exponentiation (it is XOR in Java). Final Answer: A-2, B-3, C-4, D-1

Question 15

Match adders with their time characteristics: (A) Serial binary adder, (B) Ripple-carry adder, (C) Carry look-ahead (CLA) adder — with (1) (2n − 1) * tpd, (2) (n − 1) * tpd, (3) Operation time approximately independent of size, (4) ≈ 6 * tpd for a 4…

Accepted Answer

Introduction: Adder architectures trade off speed, hardware, and control complexity. This question contrasts serial, ripple-carry, and carry look-ahead (CLA) adders using representative propagation-time models expressed in units of gate delay tpd. Given Data / Assumptions: Serial adder processes one bit per cycle with carry feedback. Ripple-carry adder propagates carry linearly through stages. CLA uses parallel carry generation/propagation to shorten delay (e.g., typical 4-bit CLA ≈ 6 * tpd). Mappings offered include (1) (2n − 1) * tpd, (2) (n − 1) * tpd, (4) 6 * tpd for 4-bit CLA. Concept / Approach: Serial adders incur sequential cycles; a representative cumulative timing is proportional to n (often modeled near (2n − 1) * tpd including setup/feedback). Ripple-carry adders have worst-case delay set by carry propagating through (n − 1) full-adder stages. CLA short-circuits the linear chain via generate/propagate logic; in classic 4-bit groups, a commonly cited figure is around 6 * tpd. Step-by-Step Solution: A → (1): Serial adder total time scales as O(n), often approximated by (2n − 1) * tpd.B → (2): Ripple-carry worst-case delay ≈ (n − 1) * tpd.C → (4): 4-bit CLA designed to deliver ≈ 6 * tpd delay figure. Verification / Alternative check: Timing textbooks and gate-level analyses agree on linear versus accelerated carry timing; CLA groups reduce depth drastically compared with ripple chains. Why Other Options Are Wrong: Any answer placing ripple at (2n − 1)*tpd or serial at (n − 1)*tpd contradicts their known timing behavior; mapping CLA to size-independent timing is a qualitative statement, whereas the option provides a specific 4-bit figure. Common Pitfalls: Confusing per-bit serial timing with combinational critical-path delay; forgetting that CLA implementations vary but remain far faster than ripple for wider words. Final Answer: A-1, B-2, C-4

Question 16

Match the control/measurement elements with their roles: (A) Synchro, (B) Amplidyne, (C) Servo, (D) RC network — with (1) Amplifier, (2) Actuator, (3) Compensator, (4) Transducer.

Accepted Answer

Introduction: Classical control systems use sensing, actuation, amplification, and compensation blocks. Recognizing each device’s role is key to reading block diagrams and designing stable loops. Given Data / Assumptions: Synchro — electromechanical angular sensor. Amplidyne — high-gain electromechanical amplifier. Servo — actuator for precise position/velocity control. RC network — analog compensator (lead/lag). Concept / Approach: A synchro converts shaft angle to electrical signals, i.e., a transducer. An amplidyne is a controlled DC generator delivering amplified power, hence an amplifier. A servo mechanism (servo motor + control) produces motion/force, serving as an actuator. RC networks shape loop frequency response to improve stability and performance, i.e., compensators. Step-by-Step Solution: A → (4): Synchro as a transducer of angular position.B → (1): Amplidyne provides power amplification.C → (2): Servo acts to move/position the plant.D → (3): RC network implements lead/lag compensation. Verification / Alternative check: Standard control texts classify sensors (transducers), actuators, amplifiers, and compensators similarly; Bode plots of RC networks exhibit lead/lag shaping. Why Other Options Are Wrong: Swapping roles misrepresents device physics: e.g., a synchro does not amplify; a servo is not a compensator; an RC network does not act as a power actuator. Common Pitfalls: Confusing servo controller electronics with the actuator itself; assuming any sensor is an actuator. Final Answer: A-4, B-1, C-2, D-3

Question 17

Match octal numbers to their decimal equivalents: (A) 35₈, (B) 65₈, (C) 54₈, (D) 76₈ — with (1) 53, (2) 62, (3) 29, (4) 44.

Accepted Answer

Introduction: Base conversion is foundational in digital systems. This problem reinforces converting from octal (base 8) to decimal (base 10) using positional weights. Given Data / Assumptions: Digits are 0–7 in octal. Weighting: the rightmost digit has weight 8^0 = 1, next is 8^1 = 8, etc. Target decimal values: 29, 53, 44, 62. Concept / Approach: For a two-digit octal ab₈, decimal value is a8 + b. Apply the same logic digit-wise for longer numbers using powers of 8. Step-by-Step Solution: Compute 35₈: 38 + 5 = 24 + 5 = 29 → (3).Compute 65₈: 68 + 5 = 48 + 5 = 53 → (1).Compute 54₈: 58 + 4 = 40 + 4 = 44 → (4).Compute 76₈: 78 + 6 = 56 + 6 = 62 → (2). Verification / Alternative check: Cross-check by reversing: 29 → 83 + 5 (digits within 0–7), etc., confirming valid octal representations. Why Other Options Are Wrong: Any mismatch indicates arithmetic or base-weighting errors (e.g., using base 10 weights). Common Pitfalls: Using base-10 weights; allowing digits 8 or 9 in octal; swapping digit order when multiplying by 8. Final Answer: A-3, B-1, C-4, D-2

Question 18

Match oscillator types to their characteristic features: (A) Wien Bridge, (B) Colpitt’s, (C) Hartley, (D) Clapp — with (1) RF oscillator using two inductors and one capacitor, (2) RF oscillator using three capacitances and one inductance, (3) RC osc…

Accepted Answer

Introduction: Oscillator categorization hinges on the frequency-determining network. Recognizing RC vs LC topologies and how inductors/capacitors are arranged is critical for selecting an appropriate oscillator for audio or RF applications. Given Data / Assumptions: Wien Bridge: bridge-type RC network, low distortion, audio-range. Colpitt’s: LC with capacitive divider (two capacitors, one inductor). Hartley: LC with inductive divider (two inductors or tapped inductor, one capacitor). Clapp: modified Colpitt’s with an additional series capacitor improving frequency stability. Concept / Approach: RC oscillators (e.g., Wien Bridge) dominate audio/low-frequency generation. LC oscillators (Colpitt’s, Hartley, Clapp) target RF. The component split (capacitive vs inductive division) distinguishes Colpitt’s and Hartley; Clapp introduces a third capacitance in series to refine stability and reduce dependence on transistor/internal capacitances. Step-by-Step Solution: A → (3): Wien Bridge is an RC audio oscillator.B → (4): Colpitt’s uses two capacitors and one inductor.C → (1): Hartley uses two inductors (or a tapped inductor) and one capacitor.D → (2): Clapp is an RF LC oscillator with three capacitors and one inductor. Verification / Alternative check: Standard oscillator tables list these associations; frequency equations confirm RC vs LC dependencies. Why Other Options Are Wrong: Swapping Colpitt’s and Hartley confuses divider type; assigning Wien Bridge to RF ignores its RC nature. Common Pitfalls: Assuming any LC is interchangeable; overlooking Clapp’s extra series capacitor and its benefit to frequency stability. Final Answer: A-3, B-4, C-1, D-2

Question 19

Match solid-state devices to their typical applications: (A) Zener diode, (B) Tunnel diode, (C) LED, (D) Photovoltaic cell — with (1) Used in seven-segment displays, (2) Used in voltage regulator circuits, (3) Used in solar energy utilization, (4) U…

Accepted Answer

Introduction: Many diodes have specialized structures that make them ideal for particular applications. Knowing these associations speeds up component selection and circuit reasoning during design and troubleshooting. Given Data / Assumptions: Zener diodes provide near-constant voltage over a range of currents (reverse breakdown). Tunnel diodes exploit negative resistance for very high-speed switching/oscillation. LEDs emit visible/IR light, commonly used in segment displays. Photovoltaic cells convert light to electrical energy. Concept / Approach: Zener → voltage regulation/reference. Tunnel diode → microwave/high-speed/digital circuits due to negative differential resistance. LED → segment/panel indicators. PV cell → solar energy harvesting. Step-by-Step Solution: A → (2): Zener in shunt regulators and references.B → (4): Tunnel diode in fast logic/oscillators.C → (1): LED segments in seven-segment displays.D → (3): Photovoltaic cells in solar utilization. Verification / Alternative check: Datasheets and application notes align with these standard uses; lab kits and textbooks show Zener regulation, LED display drivers, and PV demos. Why Other Options Are Wrong: Swapping these roles contradicts device physics (e.g., LEDs are emitters, not regulators; Zeners do not act as detectors/generators of light). Common Pitfalls: Confusing tunnel diodes with Schottky or PIN diodes; mixing photovoltaic (power generation) with photodiodes (detection). Final Answer: A-2, B-4, C-1, D-3

Question 20

Match the following in power electronics and semiconductor devices: (A) DIAC, (B) TRIAC, (C) SIT (Static Induction Transistor), (D) LASCR (Light-Activated Silicon Controlled Rectifier) — pair each with its most appropriate description or typical app…

Accepted Answer

Introduction / Context: This matching problem tests recognition of four classic semiconductor switching devices frequently encountered in basic power electronics and AC control: DIAC, TRIAC, SIT, and LASCR. Understanding what each device fundamentally is and where it is used helps students quickly select the right component for triggering, bidirectional control, high-speed switching, or optical isolation. Given Data / Assumptions: DIAC: a bidirectional trigger device used to fire TRIACs. TRIAC: a bidirectional thyristor for AC power control. SIT: Static Induction Transistor, a high-speed, majority-carrier device. LASCR: Light-Activated SCR, an SCR gated by light for isolation/safety. Concept / Approach: Associate each acronym with its defining behavior: triggering (DIAC), bidirectional AC control (TRIAC), high-speed power switching (SIT), and optically triggered thyristor action (LASCR). Step-by-Step Solution: A (DIAC) → primarily a trigger diode for AC; used to start conduction in TRIACs → 1.B (TRIAC) → conducts in both polarities and both quadrants for AC control → 2.C (SIT) → transistor class known for fast switching and low on-resistance → 3.D (LASCR) → a silicon-controlled rectifier sensitive to incident light → 4. Verification / Alternative check: Typical lamp dimmer circuits use a DIAC–TRIAC pair; SITs appear in specialized high-speed or high-frequency power applications; LASCRs are used where optical triggering or electrical isolation is desired. Why Other Options Are Wrong: A-4, B-2, C-3, D-1: Swaps DIAC and LASCR functions. A-1, B-4, C-2, D-3: Mislabels TRIAC as optically activated and SIT as AC bidirectional control. A-3, B-2, C-1, D-4: Assigns high-speed switching to DIAC and trigger role to SIT. Common Pitfalls: Assuming DIACs carry significant load power; they are primarily triggers. Confusing TRIAC (bidirectional) with SCR (unidirectional). Final Answer: A-1, B-2, C-3, D-4

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