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Question 1Engineering

A 4-bit ripple-carry adder adds A = 1111 and B = 0001 with carry-in 0. What 4-bit sum and final carry-out result?

  1. Sum = 0001, carry-out = 1
  2. Sum = 0000, carry-out = 1 Correct answer.
  3. Sum = 0000, carry-out = 0
  4. Sum = 1111, carry-out = 0

Explanation

1111 equals 15 and 0001 equals 1, so the true total is 16, which needs five bits. The low four bits are 0000 and the fifth bit appears as carry-out 1, which is the standard wraparound behaviour of a 4-bit adder.

Question 2Engineering

In a Boolean expression, the identity A + A·B = A is an example of which theorem?

  1. Absorption Correct answer.
  2. Duality
  3. Consensus
  4. De Morgan

Explanation

The absorption theorem states that A + A·B = A and its dual A·(A + B) = A, because the term B cannot change the outcome once A is true. It removes redundant terms during simplification.

Question 3Engineering

A J-K flip-flop has J = 1 and K = 1 and is clocked repeatedly. What does the output do on each active clock edge?

  1. Holds its value
  2. Sets to 1
  3. Toggles Correct answer.
  4. Clears to 0

Explanation

When both J and K are high the flip-flop operates in toggle mode, so each active clock edge complements the stored state. This is the basis for building ripple and synchronous counters from J-K devices.

Question 4Engineering

A 3-stage ring oscillator uses inverters with propagation delay 2 ns each. What is the oscillation period?

  1. 18 ns
  2. 12 ns Correct answer.
  3. 2 ns
  4. 6 ns

Explanation

A ring oscillator needs an odd number of inversions, and one full period requires the signal to travel around the loop twice, so period = 2 × N × t_pd. With N = 3 and t_pd = 2 ns the period is 2 × 3 × 2 = 12 ns.

Question 5Engineering

Which device is the primary building block of a static random-access memory cell?

  1. Dynamic capacitor
  2. Sense amplifier
  3. Cross-coupled inverters Correct answer.
  4. Floating-gate transistor

Explanation

An SRAM cell stores a bit in a bistable latch formed by two cross-coupled inverters, which hold the value as long as power is applied. This is why SRAM needs no refresh but consumes more area per bit than DRAM.

Question 6Engineering

In a MOS transistor, what is the body effect?

  1. An increase in mobility caused by a stronger vertical field
  2. A rise in drain current caused by channel-length modulation
  3. An increase in threshold voltage when the source-to-body voltage is reverse biased Correct answer.
  4. A decrease in gate capacitance at high frequency

Explanation

When the source is at a higher potential than the body, the source-body junction is reverse biased, widening the depletion region and raising the threshold voltage. This body effect degrades performance in stacked transistor networks.

Question 7Engineering

Which quantity is the Laplace transform of the unit step function u(t)?

  1. e^(-s)
  2. 1/s²
  3. 1/s Correct answer.
  4. s

Explanation

The Laplace transform of the unit step is the integral of e^(-st) from zero to infinity, which evaluates to 1/s for s with positive real part. It is the basic building block for transforms of delayed and ramp signals.

Question 8Engineering

A silicon p-n junction diode is forward biased. Which statement describes the depletion region?

  1. It narrows and the diffusion current dominates Correct answer.
  2. It widens and the drift current dominates
  3. It widens and the barrier potential increases
  4. It stays constant while both currents are equal

Explanation

Forward bias lowers the potential barrier, so the depletion width shrinks and majority-carrier diffusion across the junction grows exponentially. The small drift current remains roughly constant, so diffusion dominates.

Question 9Engineering

A transconductance amplifier has input voltage 20 mV and output current 4 mA. What is its transconductance?

  1. 80 S
  2. 5 S
  3. 0.08 S
  4. 0.2 S Correct answer.

Explanation

Transconductance is the ratio of output current to input voltage, so Gm = 4 mA / 20 mV = 0.2 S. It expresses how efficiently the amplifier converts an input voltage into an output current.

Question 10Engineering

In 8085 assembly, the instruction MOV A, M copies data from which location into the accumulator?

  1. The memory byte addressed by the H-L register pair Correct answer.
  2. The stack location pointed to by the stack pointer
  3. The immediate operand following the opcode
  4. The memory byte addressed by the program counter

Explanation

In the 8085, the register specifier M denotes memory addressed by the H-L pair, so MOV A, M performs a load from that address into A. It is a register-indirect memory access, not an immediate or stack operation.

Question 11Engineering

A 4-to-1 multiplexer has select lines S1 S0 = 10 and data inputs D0 = 1, D1 = 0, D2 = 1, D3 = 0. What is the output?

  1. 1 Correct answer.
  2. 0
  3. Undefined
  4. S1

Explanation

The select code 10 is binary 2, so the multiplexer routes input D2 to the output. Since D2 = 1, the output is 1 regardless of the other data inputs.

Question 12Engineering

A synchronous counter uses three flip-flops. What is the maximum number of distinct states it can sequence through before repeating?

  1. 8 Correct answer.
  2. 6
  3. 3
  4. 7

Explanation

Three flip-flops provide 2³ = 8 distinct binary states, so a counter can cycle through at most eight states before returning to its start. Modulo-N counters deliberately skip some of these states.

Question 13Engineering

In a common-source MOSFET amplifier with a resistive load, the small-signal voltage gain magnitude is approximately which quantity?

  1. gm divided by the load resistance
  2. The load resistance divided by gm
  3. The output resistance alone
  4. gm times the parallel combination of drain resistance and load Correct answer.

Explanation

The small-signal model gives a controlled current gm·vgs flowing into the parallel combination of the drain resistor and the external load, so the gain magnitude is gm·(RD || RL). The minus sign in the full expression reflects phase inversion.

Question 14Engineering

A 6-bit successive-approximation ADC has full-scale range 3.3 V. What is the approximate resolution?

  1. 13 mV
  2. 52 mV Correct answer.
  3. 26 mV
  4. 103 mV

Explanation

Resolution equals full-scale voltage divided by 2^N, so 3.3 V / 64 ≈ 0.052 V, or about 52 mV per LSB. This is the smallest voltage change the converter can distinguish.

Question 15Engineering

An ideal op-amp is used in an inverting configuration with input resistor 2 kΩ and feedback resistor 10 kΩ. What is the closed-loop voltage gain?

  1. −5 Correct answer.
  2. +5
  3. −0.2
  4. −12

Explanation

For the inverting amplifier the gain is −Rf/Rin = −10 kΩ / 2 kΩ = −5. The negative sign indicates a 180-degree phase inversion between input and output.

Question 16Engineering

A DC voltage source drives a series RL circuit in steady state. Which statement about the inductor is true?

  1. It dissipates power equal to V²/R
  2. It behaves as an open circuit and the current is zero
  3. It stores energy that keeps changing at a constant rate
  4. It behaves as a short circuit and the current equals V/R Correct answer.

Explanation

In DC steady state the current is constant, so the inductor voltage L·di/dt is zero and the inductor acts as a short. The current is then limited only by the series resistance, giving V/R.

Question 17Engineering

A 50 Hz sinusoidal voltage of RMS value 230 V is applied to a pure capacitor. What is the RMS current if the capacitance is 10 µF?

  1. 0.72 mA
  2. 7.2 A
  3. 0.72 A Correct answer.
  4. 0.011 A

Explanation

The capacitive reactance is 1/(2πfC) = 1/(2π × 50 × 10 µF) ≈ 318 Ω, and the current is 230/318 ≈ 0.72 A. The current leads the voltage by 90 degrees in a pure capacitor.

Question 18Engineering

A discrete-time system is described by y[n] = x[n] + x[n−1]. Which property does it have?

  1. Nonlinear and time-invariant
  2. Linear and time-invariant Correct answer.
  3. Nonlinear and time-varying
  4. Linear but time-varying

Explanation

The output is a weighted sum of input samples, so superposition holds and the system is linear. A unit shift in the input produces the identical shift in the output, so it is also time-invariant; it is a simple FIR filter.

Question 19Engineering

A bipolar junction transistor is biased in the active region. If the base-emitter voltage is increased slightly at fixed collector-emitter voltage, what happens to the collector current?

  1. It falls to zero
  2. It increases exponentially Correct answer.
  3. It remains unchanged
  4. It decreases linearly

Explanation

In the active region the collector current follows the exponential relation IC ≈ IS·exp(VBE/VT), so a small increase in VBE produces a large proportional increase in current. This exponential sensitivity is why bias stability matters.

Question 20Engineering

In a CMOS inverter, what is the main consequence of narrowing the PMOS transistor while keeping the NMOS unchanged?

  1. The static power dissipation increases sharply
  2. The propagation delay becomes independent of load capacitance
  3. The switching threshold shifts toward the lower supply rail Correct answer.
  4. The switching threshold shifts toward the upper supply rail

Explanation

The switching threshold depends on the relative strengths of the pull-up and pull-down networks. Weakening the PMOS relative to the NMOS makes the inverter trip at a lower input voltage, shifting the threshold toward ground.

Question 21Engineering

A memory system uses 16-bit words and has a 1 MByte capacity. How many addressable words does it contain?

  1. 1 M
  2. 2 M
  3. 256 K
  4. 512 K Correct answer.

Explanation

One MByte is 2²⁰ bytes, and each word occupies 2 bytes, so the number of words is 2²⁰/2 = 2¹⁹ = 512 K. Address lines therefore number 19 for word addressing.

Question 22Engineering

In the 8085, which signal indicates that the processor is performing a memory read operation?

  1. IO/M low with RD low Correct answer.
  2. IO/M high with RD low
  3. ALE high with READY high
  4. IO/M low with WR low

Explanation

A memory read is identified by IO/M being low, selecting memory rather than I/O, together with RD being asserted low. The combination of these status and control signals tells peripherals what cycle is in progress.

Question 23Engineering

A CMOS gate drives a load capacitance of 50 fF and switches at 200 MHz with a supply of 1.8 V. What is the approximate dynamic power?

  1. 65 µW
  2. 32 µW Correct answer.
  3. 8 µW
  4. 16 µW

Explanation

Dynamic power is P = α·C·V²·f. With activity factor α = 1, P = 50 fF × (1.8 V)² × 200 MHz ≈ 32 µW. The activity factor reduces this when the node does not switch every cycle.

Question 24Engineering

A negative-feedback amplifier has open-loop gain A = 1000 and feedback factor β = 0.01. What is the closed-loop gain and the loop gain?

  1. About 90.9 with loop gain 10 Correct answer.
  2. About 100 with loop gain 10
  3. About 1000 with loop gain 1
  4. About 90.9 with loop gain 0.01

Explanation

Closed-loop gain is A/(1 + Aβ) = 1000/(1 + 10) ≈ 90.9, and the loop gain Aβ is 1000 × 0.01 = 10. The large loop gain is what makes the closed-loop gain close to the ideal value of 1/β.

Question 25Engineering

A system has the characteristic polynomial s³ + 2s² + 3s + 6. Using the Routh array, how many poles lie in the right half of the s-plane?

  1. Three
  2. One
  3. Zero, but the array shows a row of zeros indicating imaginary-axis roots Correct answer.
  4. Two

Explanation

The Routh array yields a row of zeros, which signals symmetric roots about the origin. Auxiliary polynomial 2s² + 6 gives roots at s = ±j√3, so no poles lie in the right half-plane, but the system is marginally stable.

Question 26Engineering

In a CMOS logic family, the logic threshold of an inverter is set primarily by which design parameter?

  1. The ratio of the PMOS to NMOS channel-width-to-length ratios Correct answer.
  2. The absolute value of the supply voltage VDD
  3. The switching frequency of the input signal
  4. The load capacitance driven by the output

Explanation

The switching threshold of a static CMOS inverter occurs where the pull-up and pull-down currents are equal, which is governed by the relative transconductance of the PMOS and NMOS devices. Since transconductance scales with the W/L ratio and mobility, the beta ratio (beta_n/beta_p) directly sets the threshold voltage. Supply voltage and load capacitance affect noise margins and delay but not the balance point itself.

Question 27Engineering

A first-order low-pass RC filter has R = 10 kΩ and C = 10 nF. At what frequency does its magnitude response fall to 1/√2 of the passband value?

  1. 15.9 kHz
  2. 159 Hz
  3. 15.9 Hz
  4. 1.59 kHz Correct answer.

Explanation

The cutoff frequency of a first-order RC low-pass filter is f_c = 1/(2πRC). Substituting R = 10^4 Ω and C = 10^-8 F gives RC = 10^-4 s, so f_c = 1/(2π × 10^-4) ≈ 1.59 kHz. This is the frequency at which the output magnitude is 1/√2 times the DC gain, corresponding to −3 dB.

Question 28Engineering

A digital system uses a 12-bit successive-approximation ADC with a 4.096 V reference. What is the quantization step size, and what is the maximum conversion error in ideal operation?

  1. 4 mV step, ±2 mV maximum error
  2. 0.5 mV step, ±0.25 mV maximum error
  3. 1 mV step, ±0.5 mV maximum error Correct answer.
  4. 2 mV step, ±1 mV maximum error

Explanation

The step size (LSB) of an n-bit ADC with full-scale reference V_ref is V_ref/2^n. Here 4.096 V/4096 = 1 mV per LSB. For an ideal quantizer the maximum error is half an LSB, i.e. ±0.5 mV, when the input is uniformly distributed between code transitions.

Question 29Engineering

A negative-feedback system has loop gain L(s) = K/(s(s+2)(s+4)). Using the Routh–Hurwitz criterion, what is the maximum value of K for which the closed-loop system remains stable?

  1. 12
  2. 24
  3. 96
  4. 48 Correct answer.

Explanation

The closed-loop characteristic polynomial is s^3 + 6s^2 + 8s + K = 0. The Routh array gives the auxiliary condition that all elements of the first column be positive, requiring K > 0 and 6·8 − K > 0, so stability holds for 0 < K < 48. The critical gain at which the system becomes marginally stable is therefore K = 48, where a pair of poles crosses the jω axis.

Question 30Technology

In a packet-switched network, which function is performed by the network layer of the OSI reference model?

  1. Logical addressing and routing of packets between networks Correct answer.
  2. Encoding of application data into a common syntax
  3. Framing of bits and error detection on a single link
  4. Reliable end-to-end delivery with flow control

Explanation

The network layer handles logical addressing and routing so packets can travel across multiple networks toward a destination. Framing and link-level error detection belong to the data link layer, while end-to-end reliability is a transport-layer concern.

Question 31Technology

A host has the IPv4 address 192.168.10.130 with subnet mask 255.255.255.192. What is the network address of its subnet?

  1. 192.168.10.0
  2. 192.168.10.128 Correct answer.
  3. 192.168.10.192
  4. 192.168.10.64

Explanation

The mask 255.255.255.192 gives a block size of 64 in the last octet, so subnets start at 0, 64, 128 and 192. The address 130 falls inside the block beginning at 128, making 192.168.10.128 the network address.

Question 32Technology

Which transport protocol and port number are used by a client contacting a standard DNS server for name resolution queries?

  1. TCP port 53
  2. UDP port 123
  3. TCP port 25
  4. UDP port 53 Correct answer.

Explanation

Ordinary DNS queries and responses use UDP on port 53 because the request-response exchange is small and connectionless. TCP port 53 is reserved for zone transfers and responses too large for UDP.

Question 33Technology

Which device forwards frames based on MAC addresses and confines collision domains to individual ports?

  1. Layer 2 switch Correct answer.
  2. Repeater
  3. Hub
  4. Router

Explanation

A Layer 2 switch learns MAC addresses and forwards frames only out of the port toward the destination, giving each port its own collision domain. Hubs and repeaters simply regenerate signals to all ports, sharing one collision domain.

Question 34Technology

In the TCP three-way handshake, what does the client send in the second step of the exchange as seen from the server's perspective?

  1. SYN with a new initial sequence number
  2. SYN and ACK together, with the server's own initial sequence number Correct answer.
  3. ACK only, acknowledging the server's sequence number
  4. FIN and ACK together, closing the half-open connection

Explanation

The handshake proceeds SYN from the client, then SYN-ACK from the server, then ACK from the client. The SYN-ACK carries the server's initial sequence number and acknowledges the client's SYN.

Question 35Technology

Which statement describes the behaviour of a Class A private address range as defined in RFC 1918?

  1. 10.0.0.0/8 is reserved for private use and is not routed on the public Internet Correct answer.
  2. 172.16.0.0/12 is a Class A private range
  3. 192.168.0.0/16 is a Class A private range
  4. 127.0.0.0/8 is a Class A private range used for internal hosts

Explanation

RFC 1918 designates 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 as private ranges that Internet routers do not forward. Only 10.0.0.0/8 falls in the historical Class A space.

Question 36Technology

Which medium access method does IEEE 802.11 use to coordinate contention among wireless stations in a basic service set?

  1. Deterministic priority queuing by frame type
  2. Time division multiplexing with fixed slots
  3. Token passing coordinated by the access point
  4. Carrier sense multiple access with collision avoidance Correct answer.

Explanation

Wireless stations cannot reliably detect collisions, so 802.11 uses CSMA/CA with random backoff and optional request-to-send/clear-to-send exchange. Token passing and fixed slotting are used in other technologies, not in standard 802.11 contention.

Question 37Technology

A network administrator needs a cable that supports 1 Gbps over 100 metres in a new horizontal cabling run. Which cable category is the minimum standard choice?

  1. Cat 7 STP
  2. Cat 5e UTP Correct answer.
  3. Cat 3 UTP
  4. Cat 5 UTP

Explanation

Cat 5e is specified for 1000BASE-T over 100 metres and is the minimum category commonly accepted for gigabit horizontal cabling. Cat 5 was designed for 100BASE-TX, while Cat 3 supports only 10 Mbps Ethernet.

Question 38Technology

Which field in an IPv4 header prevents packets from looping indefinitely in a network with a routing error?

  1. Fragment offset
  2. Type of Service
  3. Header checksum
  4. Time to Live Correct answer.

Explanation

Each router decrements the Time to Live field, and a packet is discarded with an ICMP Time Exceeded message when the value reaches zero. This bounds the lifetime of a packet even when routing tables contain a loop.

Question 39Technology

An organisation is assigned 200.10.4.0/22. How many usable host addresses does this block provide for standard subnet assignment?

  1. 2046
  2. 510
  3. 1024
  4. 1022 Correct answer.

Explanation

A /22 leaves 10 host bits, giving 2^10 = 1024 addresses in the block. Subtracting the network and broadcast addresses leaves 1022 usable host addresses.

Question 40Technology

A router receives a packet destined for 172.20.5.9 and has these routes: 0.0.0.0/0 via 10.1.1.1, 172.20.0.0/16 via 10.1.1.2, and 172.20.5.0/24 via 10.1.1.3. Which next hop is selected?

  1. 10.1.1.1
  2. The packet is dropped because of ambiguity
  3. 10.1.1.3 Correct answer.
  4. 10.1.1.2

Explanation

Longest prefix match governs forwarding when several routes match the destination. The /24 route is more specific than the /16 and default routes, so the packet goes to 10.1.1.3.

Question 41Technology

Which mechanism allows a host to learn the MAC address associated with a known IPv4 address on the local link?

  1. Reverse DNS lookup through the resolver
  2. ARP broadcast request and unicast reply Correct answer.
  3. ICMP redirect from the default gateway
  4. DHCP discover and offer exchange

Explanation

ARP broadcasts a request asking which station owns the target IPv4 address, and the owner replies directly with its MAC address. DHCP assigns addresses, while reverse DNS maps addresses to names, not to link-layer addresses.

Question 42Technology

In a VLAN trunk using IEEE 802.1Q, what is the purpose of the tag inserted into the Ethernet frame?

  1. It identifies the VLAN membership of the frame Correct answer.
  2. It records the frame check sequence for the trunk
  3. It stores the source MAC address for learning
  4. It carries the IP precedence value for quality of service

Explanation

The 802.1Q tag includes a 12-bit VLAN identifier so a switch can keep traffic for different VLANs separate on a shared trunk. Priority bits exist in the tag, but the tag's primary role is VLAN identification.

Question 43Technology

Which OSPF packet type is used by a router to confirm that a neighbour is reachable and to detect failure of the adjacency?

  1. Link State Acknowledgement
  2. Hello Correct answer.
  3. Database Description
  4. Link State Update

Explanation

OSPF routers send Hello packets periodically on each interface, and failure to receive them within the dead interval tears down the adjacency. The other packet types carry database synchronisation information.

Question 44Technology

A network uses NAT overload on a single public address. Which combination uniquely identifies a translated session in the NAT table?

  1. Destination MAC address and source MAC address
  2. Source IP address and destination port only
  3. Inside local IP address and inside local port
  4. Inside local IP address, inside local port, and protocol Correct answer.

Explanation

Port address translation distinguishes sessions by the internal address, internal port and protocol tuple before mapping them to the public address and a translated port. Without the protocol and port, two hosts using the same internal port could not be told apart.

Question 45Technology

Which statement correctly describes the difference between symmetric and asymmetric encryption in network security?

  1. Symmetric uses a public key, while asymmetric uses a shared secret
  2. Symmetric keys are always longer than asymmetric keys
  3. Symmetric uses one shared key, while asymmetric uses a public and private key pair Correct answer.
  4. Symmetric provides non-repudiation, while asymmetric cannot

Explanation

Symmetric algorithms such as AES use a single shared key for encryption and decryption. Asymmetric algorithms such as RSA use a mathematically related key pair, which also enables digital signatures.

Question 46Technology

A firewall rule set processes packets top-down and stops at the first match. Given the rules: 1 permit tcp any any eq 80; 2 deny tcp any any; 3 permit ip any any, what happens to an inbound HTTP request to port 80?

  1. It is permitted by rule 3
  2. It is denied by rule 2
  3. It is permitted by rule 1 Correct answer.
  4. It is logged and dropped by default policy

Explanation

Because rules are evaluated in order and evaluation stops at the first match, the HTTP packet matches rule 1 and is permitted. Rules 2 and 3 are never reached for this traffic.

Question 47Technology

Which protocol provides a secure, encrypted interactive terminal session and typically listens on TCP port 22?

  1. Telnet
  2. SSH Correct answer.
  3. TFTP
  4. SNMP

Explanation

SSH encrypts the session and authenticates the server, protecting credentials and data in transit on TCP port 22. Telnet offers a similar service but sends everything in cleartext.

Question 48Technology

A subnet uses the mask 255.255.255.224. What is the broadcast address of the subnet containing host 10.5.5.100?

  1. 10.5.5.111
  2. 10.5.5.127 Correct answer.
  3. 10.5.5.95
  4. 10.5.5.128

Explanation

The mask 255.255.255.224 gives blocks of 32, so the subnet containing 100 runs from 10.5.5.96 to 10.5.5.127. The last address in that range, 10.5.5.127, is the broadcast address.

Question 49Technology

Which IPv6 address type is used for one-to-nearest delivery, where the packet is routed to the closest member of an anycast group?

  1. Multicast
  2. Unicast
  3. Broadcast
  4. Anycast Correct answer.

Explanation

Anycast delivers to the nearest member of a group according to routing distance, which is useful for services such as root DNS servers. IPv6 has no broadcast type, and multicast delivers to all members of a group.

Question 50Technology

A company wants to prevent an attacker from impersonating a server during a TLS session. Which component of the protocol achieves this?

  1. The key exchange cipher suite alone
  2. The symmetric session key length
  3. The server certificate verified against a trusted certificate authority Correct answer.
  4. The compression method negotiated in the handshake

Explanation

The server presents a certificate signed by a trusted authority, and the client verifies the signature chain and the name in the certificate. This authentication step proves the server's identity before session keys are used.