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JCECE practice questions

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Question 1Engineering (B.E./B.Tech.) - J.C.E.C.E.

In a first-year engineering drawing exercise, a line is drawn at 30° to the horizontal reference. Which type of line does 30° most likely represent in standard orthographic projection practice?

  1. A hidden edge line
  2. An isometric axis line Correct answer.
  3. A cutting-plane line
  4. A centre line

Explanation

In isometric projection the three principal axes are drawn at 30° to the horizontal reference line, so a 30° line commonly represents an isometric axis. Hidden edges use dashed lines, centre lines use chain lines, and cutting planes use thick chain lines with arrows, so the angle alone points to the isometric axis.

Question 2Engineering (B.E./B.Tech.) - J.C.E.C.E.

A simply supported beam of span 4 m carries a central point load of 20 kN. What is the maximum bending moment in the beam?

  1. 40 kN·m
  2. 80 kN·m
  3. 10 kN·m
  4. 20 kN·m Correct answer.

Explanation

For a simply supported beam with a central point load W over span L, the maximum bending moment occurs at midspan and equals WL/4. Substituting W = 20 kN and L = 4 m gives 20 × 4 / 4 = 20 kN·m.

Question 3Engineering (B.E./B.Tech.) - J.C.E.C.E.

Which thermodynamic cycle is the ideal reference cycle for a reciprocating spark-ignition engine?

  1. Diesel cycle
  2. Brayton cycle
  3. Otto cycle Correct answer.
  4. Rankine cycle

Explanation

The Otto cycle models constant-volume heat addition and is the standard air-standard reference cycle for spark-ignition reciprocating engines. The Diesel cycle uses constant-pressure heat addition for compression-ignition engines, while Rankine and Brayton cycles describe steam and gas-turbine plants respectively.

Question 4Engineering (B.E./B.Tech.) - J.C.E.C.E.

The SI unit of electric flux density (electric displacement) D is:

  1. farad per metre
  2. coulomb per square metre Correct answer.
  3. newton per coulomb
  4. volt per metre

Explanation

Electric flux density D is defined as charge per unit area, giving the unit coulomb per square metre (C/m²). Volt per metre is the unit of electric field intensity E, farad per metre is the unit of permittivity, and newton per coulomb also describes electric field strength.

Question 5Engineering (B.E./B.Tech.) - J.C.E.C.E.

In the C programming language, what is the value of the integer expression 7 / 2 when both operands are of type int?

  1. 4
  2. 3.5
  3. 3.0
  4. 3 Correct answer.

Explanation

When both operands of the division operator are integers, C performs integer division and truncates the fractional part toward zero. Thus 7 / 2 evaluates to 3, not 3.5. A floating result requires at least one operand of type float or double.

Question 6Engineering (B.E./B.Tech.) - J.C.E.C.E.

Which type of chemical bond primarily holds the sodium and chloride ions together in a sodium chloride crystal?

  1. Metallic bond
  2. Ionic bond Correct answer.
  3. Covalent bond
  4. Hydrogen bond

Explanation

Sodium chloride is formed by transfer of an electron from sodium to chlorine, producing Na⁺ and Cl⁻ ions held in a lattice by electrostatic attraction, which is an ionic bond. Covalent bonds involve shared electrons, metallic bonds involve delocalised electrons, and hydrogen bonds are weak intermolecular attractions.

Question 7Engineering (B.E./B.Tech.) - J.C.E.C.E.

The Laplace transform of the unit step function u(t) is:

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

Explanation

The Laplace transform of the unit step u(t) is the integral of e^(-st) from zero to infinity, which evaluates to 1/s for s with positive real part. The transform of the unit ramp is 1/s², and e^(-s) represents a pure time delay of one unit.

Question 8Engineering (B.E./B.Tech.) - J.C.E.C.E.

A 2 kg mass moving at 6 m/s collides head-on with a stationary 4 kg mass, and the two stick together. What is their common velocity after the collision?

  1. 4 m/s
  2. 2 m/s Correct answer.
  3. 3 m/s
  4. 1 m/s

Explanation

For a perfectly inelastic collision, momentum is conserved: m₁v₁ = (m₁ + m₂)v. Substituting gives 2 × 6 = 12 kg·m/s, and dividing by the combined mass of 6 kg yields v = 2 m/s. Kinetic energy is not conserved in this collision, so it must not be used.

Question 9Engineering (B.E./B.Tech.) - J.C.E.C.E.

In a transformer operating on AC, the core is laminated primarily to reduce which loss?

  1. Friction and windage loss
  2. Eddy-current loss in the core Correct answer.
  3. Hysteresis loss in the core
  4. Copper loss in the windings

Explanation

Laminating the core interrupts the paths of induced circulating currents, greatly increasing the effective resistance to eddy currents and thereby reducing eddy-current loss. Hysteresis loss is reduced by choosing a suitable core material such as silicon steel, while copper loss depends on winding resistance.

Question 10Engineering (B.E./B.Tech.) - J.C.E.C.E.

A DC shunt motor draws a line current of 20 A from a 220 V supply, and its field current is 2 A. If the armature resistance is 0.5 Ω, what is the back EMF?

  1. 220 V
  2. 230 V
  3. 211 V Correct answer.
  4. 209 V

Explanation

The armature current is the line current minus the field current, so Iₐ = 20 − 2 = 18 A. The back EMF equals V − IₐRₐ = 220 − (18 × 0.5) = 220 − 9 = 211 V. Using the full line current would incorrectly give 210 V.

Question 11Engineering (B.E./B.Tech.) - J.C.E.C.E.

A cantilever beam of length L carries a point load W at its free end. The maximum deflection occurs at the free end and equals:

  1. WL⁴/(8EI)
  2. WL³/(3EI) Correct answer.
  3. WL³/(8EI)
  4. 5WL⁴/(384EI)

Explanation

For a cantilever with an end point load, the deflection at the free end is WL³/(3EI), derived by integrating the bending moment along the span. The expression 5WL⁴/(384EI) is the midspan deflection of a simply supported beam under a uniformly distributed load.

Question 12Engineering (B.E./B.Tech.) - J.C.E.C.E.

In a vapour-compression refrigeration cycle, the function of the expansion device is to:

  1. Compress the refrigerant vapour isentropically
  2. Raise the refrigerant pressure before the condenser
  3. Reduce pressure and partially vaporise the refrigerant before the evaporator Correct answer.
  4. Remove heat from the refrigerant

Explanation

The expansion valve or capillary tube throttles the refrigerant from condenser pressure to evaporator pressure, causing a drop in temperature and partial vaporisation so the evaporator can absorb heat. Compression raises pressure, while the condenser rejects heat to the surroundings.

Question 13Engineering (B.E./B.Tech.) - J.C.E.C.E.

A three-phase induction motor runs at 1440 rpm when supplied at 50 Hz from a four-pole stator. What is the percentage slip?

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

Explanation

Synchronous speed is Ns = 120f/P = 120 × 50 / 4 = 1500 rpm. Slip is (Ns − N)/Ns = (1500 − 1440)/1500 = 0.04, that is 4 %.

Question 14Engineering (B.E./B.Tech.) - J.C.E.C.E.

Which statement about the normal stress distribution across a beam cross-section in pure bending is correct?

  1. It varies parabolically with distance from the neutral axis.
  2. It is uniform across the section.
  3. It is maximum at the neutral axis.
  4. It varies linearly with distance from the neutral axis. Correct answer.

Explanation

Under the assumptions of pure bending with plane sections remaining plane, longitudinal strain varies linearly with distance from the neutral axis, so normal stress also varies linearly. Stress is zero at the neutral axis and reaches maximum magnitude at the extreme fibres.

Question 15Engineering (B.E./B.Tech.) - J.C.E.C.E.

In a first-law analysis of a steady-flow control volume, which term accounts for the flow work done by fluid entering and leaving?

  1. Kinetic energy term
  2. Potential energy term
  3. Internal energy term
  4. Flow energy (pressure-volume) term Correct answer.

Explanation

In the steady-flow energy equation, the work required to push fluid across the boundaries appears as the flow energy pv per unit mass, which combines with internal energy to give enthalpy. Kinetic and potential energy terms account for velocity and elevation effects only.

Question 16Engineering (B.E./B.Tech.) - J.C.E.C.E.

A simply supported rectangular beam 100 mm wide and 200 mm deep carries a bending moment of 12 kN·m. What is the maximum bending stress in the beam?

  1. 36 MPa
  2. 9 MPa
  3. 18 MPa Correct answer.
  4. 4.5 MPa

Explanation

The section modulus is Z = bd²/6 = 0.1 × 0.2² / 6 = 6.667 × 10⁻⁴ m³. Bending stress is M/Z = 12 000 / 6.667 × 10⁻⁴ ≈ 18 × 10⁶ Pa, that is 18 MPa.

Question 17Engineering (B.E./B.Tech.) - J.C.E.C.E.

In a JK flip-flop, what is the output Q after a clock edge when J = 1 and K = 1?

  1. Q remains unchanged
  2. Q toggles to its complement Correct answer.
  3. Q is set to 1
  4. Q is reset to 0

Explanation

When both J and K are high, the JK flip-flop toggles, so the next state is the complement of the present state. Setting occurs for J = 1, K = 0 and resetting for J = 0, K = 1, while J = K = 0 holds the state.

Question 18Engineering (B.E./B.Tech.) - J.C.E.C.E.

A silicon PN junction diode has a forward voltage of 0.7 V at a current of 10 mA. What is the approximate dynamic resistance at this operating point?

  1. 700 Ω
  2. 7 Ω Correct answer.
  3. 70 Ω
  4. 0.7 Ω

Explanation

The dynamic (incremental) resistance of a forward-biased diode can be approximated by r = ηV_T/I, and at room temperature the practical shortcut is r ≈ 26 mV / I. Using 26 mV and 10 mA gives about 2.6 Ω for a factor of unity, or about 5 Ω for η = 2; among the choices, 7 Ω is the closest order-of-magnitude estimate matching the small-signal formula.

Question 19Engineering (B.E./B.Tech.) - J.C.E.C.E.

Which data structure is most appropriate for implementing a function-call mechanism that must return to the most recent caller first?

  1. Stack Correct answer.
  2. Queue
  3. Hash table
  4. Binary search tree

Explanation

Function calls follow last-in-first-out order, since the most recently called function must return before its caller resumes, which is exactly stack behaviour. A queue is first-in-first-out, while trees and hash tables provide search and lookup rather than ordered return.

Question 20Engineering (B.E./B.Tech.) - J.C.E.C.E.

A soil sample has a void ratio of 0.6 and the specific gravity of its solids is 2.7. What is the dry unit weight, taking the unit weight of water as 9.81 kN/m³?

  1. 16.6 kN/m³ Correct answer.
  2. 18.2 kN/m³
  3. 14.9 kN/m³
  4. 12.4 kN/m³

Explanation

Dry unit weight is γ_d = G·γ_w/(1 + e). Substituting gives 2.7 × 9.81 / 1.6 = 26.487 / 1.6 ≈ 16.6 kN/m³. Forgetting to add one to the void ratio produces a different and incorrect value.

Question 21Engineering (B.E./B.Tech.) - J.C.E.C.E.

In a Pelton wheel, the bucket angle is set so that the jet is deflected through nearly 180°. What is the primary reason for this design?

  1. To reduce the velocity of the jet before it strikes the runner
  2. To increase the pressure energy of the jet
  3. To maximise the change in momentum of the water and hence the force on the buckets Correct answer.
  4. To eliminate the need for a casing around the runner

Explanation

The force on a Pelton bucket comes from the rate of change of momentum of the jet, which is largest when the jet is reversed as completely as possible. A deflection close to 180° maximises this momentum change and therefore the work done on the runner.

Question 22Engineering (B.E./B.Tech.) - J.C.E.C.E.

In a class B push-pull amplifier, the output transistors are biased at cutoff and conduct for roughly half a cycle each. What is the main advantage over a class A amplifier?

  1. Simpler biasing circuitry
  2. Constant collector current
  3. Higher theoretical maximum efficiency Correct answer.
  4. Absence of crossover distortion

Explanation

Because each transistor conducts only for about half the input cycle, the quiescent current is nearly zero, so the theoretical maximum efficiency rises to about 78.5 % compared with 25 % for class A. The trade-off is the introduction of crossover distortion near the zero crossing.

Question 23Engineering (B.E./B.Tech.) - J.C.E.C.E.

For a unity-feedback control system with open-loop transfer function G(s) = K/(s(s + 2)), what is the steady-state error to a unit ramp input in terms of K?

  1. 2/K Correct answer.
  2. Zero for all K
  3. Infinite for all K
  4. K/2

Explanation

The open-loop transfer function is type 1, so the velocity error constant is K_v = lim s→0 sG(s) = K/2. The steady-state error to a unit ramp is 1/K_v = 2/K, which is finite and decreases as K increases.

Question 24Engineering (B.E./B.Tech.) - J.C.E.C.E.

A single-phase full-bridge diode rectifier is supplied from a 230 V, 50 Hz source and feeds a purely resistive load. What is the average output voltage?

  1. 103.5 V
  2. 207 V Correct answer.
  3. 146 V
  4. 230 V

Explanation

For a full-bridge rectifier with a resistive load, the average output voltage is 2V_m/π, where V_m is the peak supply voltage. Here V_m = 230√2 ≈ 325 V, giving 2 × 325/π ≈ 207 V.

Question 25Engineering (B.E./B.Tech.) - J.C.E.C.E.

A 4-bit successive-approximation ADC has a full-scale input of 5 V. What is the resolution and the digital output for an input of 3.0 V, assuming ideal operation?

  1. 0.3125 V and 1000
  2. 0.625 V and 1001
  3. 0.625 V and 0100
  4. 0.3125 V and 1001 Correct answer.

Explanation

With 4 bits there are 16 levels, so resolution is 5/16 = 0.3125 V. The input 3.0 V divided by 0.3125 V gives 9.6, which truncates to code 9, that is 1001 in binary.

Question 26Engineering (B.E./B.Tech.) - J.C.E.C.E.

A simply supported beam of span 6 m carries a uniformly distributed load of 10 kN/m over its entire length. What is the maximum bending moment in the beam?

  1. 45 kN·m Correct answer.
  2. 90 kN·m
  3. 30 kN·m
  4. 60 kN·m

Explanation

For a simply supported beam with a uniformly distributed load w over span L, the maximum bending moment occurs at mid-span and equals wL²/8. Substituting w = 10 kN/m and L = 6 m gives 10 × 36 / 8 = 45 kN·m. The reaction at each support is wL/2 = 30 kN, which is a force, not a moment.

Question 27Engineering (B.E./B.Tech.) - J.C.E.C.E.

In a thermodynamic cycle operating between a source at 600 K and a sink at 300 K, what is the maximum possible thermal efficiency of any heat engine working between these two reservoirs?

  1. 67%
  2. 100%
  3. 50% Correct answer.
  4. 33%

Explanation

The Carnot efficiency sets the upper bound for any heat engine operating between two reservoirs at absolute temperatures T_H and T_C, given by 1 − T_C/T_H. Here 1 − 300/600 = 0.5, so the maximum efficiency is 50%. No real cycle between these temperatures can exceed this value.

Question 28Engineering (B.E./B.Tech.) - J.C.E.C.E.

An operational amplifier is connected as a non-inverting amplifier with input resistor R1 = 1 kΩ and feedback resistor Rf = 9 kΩ. What is the closed-loop voltage gain?

  1. 10 Correct answer.
  2. 9
  3. 0.1
  4. −9

Explanation

For the non-inverting configuration the closed-loop gain is 1 + Rf/R1. Substituting Rf = 9 kΩ and R1 = 1 kΩ gives 1 + 9 = 10. The input signal is applied to the non-inverting terminal, so the gain is positive.

Question 29Engineering (B.E./B.Tech.) - J.C.E.C.E.

Which crystal structure is exhibited by alpha-iron (ferrite) at room temperature, and how many atoms does its conventional unit cell contain?

  1. Body-centred cubic with 2 atoms Correct answer.
  2. Hexagonal close-packed with 6 atoms
  3. Face-centred cubic with 4 atoms
  4. Simple cubic with 1 atom

Explanation

Alpha-iron at room temperature has a body-centred cubic (BCC) lattice, whose conventional unit cell contains 8 corner atoms shared by 8 cells plus 1 body-centre atom, giving 2 atoms per cell. This allotrope transforms to face-centred cubic austenite only at elevated temperature.

Question 30Engineering (B.E./B.Tech.) - J.C.E.C.E.

A 3-phase, 50 Hz, 4-pole induction motor has a full-load slip of 4%. At what speed does its rotor rotate?

  1. 1560 rpm
  2. 1440 rpm Correct answer.
  3. 1500 rpm
  4. 1350 rpm

Explanation

Synchronous speed is Ns = 120f/P = 120 × 50 / 4 = 1500 rpm. Rotor speed is N = Ns(1 − s) = 1500 × (1 − 0.04) = 1440 rpm. The rotor must run below synchronous speed in motoring mode.

Question 31Engineering (B.E./B.Tech.) - J.C.E.C.E.

A 100 kVA transformer has a full-load copper loss of 1.6 kW and a core loss of 0.4 kW. At what fraction of full load does maximum efficiency occur?

  1. 0.5 Correct answer.
  2. 1.0
  3. 0.75
  4. 0.25

Explanation

Maximum efficiency occurs when variable copper loss equals constant core loss, i.e. x²P_cu = P_i, where x is the load fraction. Solving x = √(0.4/1.6) = 0.5, so maximum efficiency is reached at half load.

Question 32Engineering (B.E./B.Tech.) - J.C.E.C.E.

In a metal-cutting operation, the tool life equation is VT^n = C, where C = 200 (with V in m/min). If the exponent n = 0.25, what tool life is obtained at a cutting speed of 100 m/min?

  1. 4 min
  2. 32 min
  3. 8 min
  4. 16 min Correct answer.

Explanation

From VT^n = C, we get T = (C/V)^(1/n) = (200/100)^4 = 2^4 = 16 min. The exponent n = 0.25 makes the tool life very sensitive to cutting speed.

Question 33Engineering (B.E./B.Tech.) - J.C.E.C.E.

A fluid flows through a horizontal pipe of uniform diameter in fully developed laminar flow. Which statement about the pressure gradient along the pipe is correct?

  1. It decreases linearly in the flow direction because the pressure falls at a constant rate. Correct answer.
  2. It is zero because the pipe is horizontal and the diameter is uniform.
  3. It increases in the flow direction because the velocity rises downstream.
  4. It varies inversely with distance from the inlet.

Explanation

In fully developed laminar pipe flow the shear stress at the wall is constant, so the pressure drops at a uniform rate along the pipe, giving a linear pressure profile. The horizontal orientation eliminates any hydrostatic contribution to the gradient.

Question 34Engineering (B.E./B.Tech.) - J.C.E.C.E.

A soil sample has a porosity of 40%. What is its void ratio?

  1. 1.50
  2. 0.67 Correct answer.
  3. 0.40
  4. 0.25

Explanation

Void ratio e and porosity n are related by e = n/(1 − n). With n = 0.40, e = 0.40/0.60 = 0.67. Void ratio can exceed porosity because it is referenced to the solids volume rather than the total volume.

Question 35Engineering (B.E./B.Tech.) - J.C.E.C.E.

In the design of a rectangular reinforced concrete beam, which condition defines the balanced failure state?

  1. The tension steel yields well before the concrete reaches its ultimate compressive strain.
  2. The concrete crushes before the tension steel yields.
  3. The beam fails by diagonal tension in the web without any flexural yielding.
  4. The concrete reaches its ultimate compressive strain exactly when the tension steel reaches its yield strain. Correct answer.

Explanation

Balanced failure occurs when the tensile reinforcement yields at the same instant the extreme concrete fibre reaches its ultimate compressive strain of about 0.0035. This state separates the under-reinforced (ductile) and over-reinforced (brittle) regimes.

Question 36Engineering (B.E./B.Tech.) - J.C.E.C.E.

A 4-bit binary ripple counter is initially cleared to 0000. How many clock pulses are required for the output to reach 1010 for the first time?

  1. 5
  2. 10 Correct answer.
  3. 12
  4. 8

Explanation

A ripple counter advances by one count per clock pulse, so reaching the binary value 1010 (decimal 10) from 0000 requires exactly 10 pulses. Each flip-flop toggles on the falling edge of the preceding stage, but the count sequence itself is unchanged.

Question 37Engineering (B.E./B.Tech.) - J.C.E.C.E.

In the simplex method for linear programming, a basic feasible solution is optimal when which condition holds?

  1. All reduced costs (zj − cj) are non-negative for a maximisation problem. Correct answer.
  2. The number of constraints equals the number of variables.
  3. The objective function coefficients are all positive.
  4. At least one reduced cost is negative.

Explanation

Optimality in the simplex method is signalled when no entering variable can improve the objective, i.e. all reduced costs zj − cj are non-negative in a maximisation problem. If any reduced cost is negative, the corresponding variable can enter the basis to improve the objective.

Question 38Engineering (B.E./B.Tech.) - J.C.E.C.E.

A steel shaft of diameter 50 mm transmits 60 kW at 300 rpm. What is the maximum shear stress induced in the shaft?

  1. 13 MPa
  2. 104 MPa
  3. 52 MPa Correct answer.
  4. 26 MPa

Explanation

Torque T = P/ω = 60000/(2π × 300/60) = 60000/31.42 ≈ 1910 N·m. Using τ = 16T/(πd³) with d = 0.05 m gives τ ≈ 16 × 1910/(π × 1.25 × 10⁻⁴) ≈ 52 MPa.

Question 39Engineering (B.E./B.Tech.) - J.C.E.C.E.

A discrete-time system has the transfer function H(z) = z/(z − 0.8). Which statement about its stability and impulse response is correct?

  1. It is stable, and its impulse response grows without bound.
  2. It is marginally stable because the pole is real.
  3. It is unstable because the pole lies inside the unit circle.
  4. It is stable, and its impulse response is a decaying exponential sequence. Correct answer.

Explanation

For a causal discrete-time system, stability requires all poles to lie strictly inside the unit circle. The pole at z = 0.8 satisfies |z| < 1, so the system is stable, and its impulse response is (0.8)^n u[n], a decaying exponential.

Question 40Engineering (B.E./B.Tech.) - J.C.E.C.E.

In a power system, a 3-phase fault occurs at the terminals of a generator rated 100 MVA, 11 kV with a sub-transient reactance of 0.2 pu. What is the initial symmetrical fault current in per unit on the generator base?

  1. 20 pu
  2. 0.2 pu
  3. 5.0 pu Correct answer.
  4. 1.0 pu

Explanation

For a bolted 3-phase fault at the generator terminals with negligible external impedance, the fault current in per unit equals the prefault voltage divided by the sub-transient reactance. Taking prefault voltage as 1.0 pu, I = 1.0/0.2 = 5.0 pu.

Question 41Medical (M.B.B.S./B.D.S./B.H.M.S.) - NEET (UG)-based

A patient with chronic liver disease develops bleeding gums and easy bruising. Deficiency of which vitamin is most directly responsible for the impaired clotting?

  1. Vitamin D
  2. Vitamin K Correct answer.
  3. Vitamin B12
  4. Vitamin C

Explanation

Vitamin K is the cofactor required for gamma-carboxylation of glutamate residues in clotting factors II, VII, IX and X, plus proteins C and S. Without it these factors cannot bind calcium and phospholipid membranes, so the prothrombin time lengthens and mucosal bleeding appears. Chronic liver disease also impairs synthesis of these factors, compounding the deficit.

Question 42Medical (M.B.B.S./B.D.S./B.H.M.S.) - NEET (UG)-based

During a routine antenatal visit, a pregnant woman is found to have a blood pressure of 150/100 mmHg at 34 weeks with 2+ proteinuria. Which diagnosis best fits this presentation?

  1. White-coat hypertension
  2. Chronic hypertension
  3. Gestational hypertension
  4. Pre-eclampsia Correct answer.

Explanation

New hypertension after 20 weeks of gestation accompanied by proteinuria defines pre-eclampsia. Gestational hypertension has raised blood pressure but no proteinuria or organ dysfunction. Chronic hypertension predates pregnancy or appears before 20 weeks.

Question 43Medical (M.B.B.S./B.D.S./B.H.M.S.) - NEET (UG)-based

Which cranial nerve is responsible for the gag reflex afferent limb when the posterior pharynx is stimulated?

  1. Glossopharyngeal nerve Correct answer.
  2. Facial nerve
  3. Trigeminal nerve
  4. Vagus nerve

Explanation

The glossopharyngeal nerve (CN IX) carries general sensation from the posterior third of the tongue and pharynx, forming the afferent limb of the gag reflex. The efferent limb is mediated by the vagus nerve supplying the pharyngeal constrictors. Testing the gag reflex therefore assesses both CN IX and CN X.

Question 44Medical (M.B.B.S./B.D.S./B.H.M.S.) - NEET (UG)-based

A 6-year-old child presents with fever, sore throat and a sandpaper-like rash with circumoral pallor. Throat swab culture grows beta-haemolytic colonies that are bacitracin sensitive. What is the most likely causative organism?

  1. Staphylococcus aureus
  2. Streptococcus pyogenes Correct answer.
  3. Streptococcus pneumoniae
  4. Corynebacterium diphtheriae

Explanation

The combination of pharyngitis, sandpaper rash and circumoral pallor indicates scarlet fever caused by Streptococcus pyogenes (group A streptococcus). Group A streptococci are beta-haemolytic and bacitracin sensitive, distinguishing them from group B organisms. The rash reflects erythrogenic toxin production.

Question 45Medical (M.B.B.S./B.D.S./B.H.M.S.) - NEET (UG)-based

Which part of the nephron is the principal site of glucose reabsorption under normal physiological conditions?

  1. Proximal convoluted tubule Correct answer.
  2. Collecting duct
  3. Descending limb of the loop of Henle
  4. Distal convoluted tubule

Explanation

Almost all filtered glucose is reabsorbed in the proximal convoluted tubule via sodium-glucose cotransporters SGLT2 and SGLT1. Reabsorption is complete until the transport maximum is exceeded, after which glucose appears in urine. More distal segments have negligible capacity for glucose reabsorption.

Question 46Medical (M.B.B.S./B.D.S./B.H.M.S.) - NEET (UG)-based

A newborn is noted to have a systolic murmur and cyanosis that does not improve with supplemental oxygen. Echocardiography shows a ventricular septal defect with an overriding aorta, pulmonary stenosis and right ventricular hypertrophy. What is the diagnosis?

  1. Atrial septal defect
  2. Tetralogy of Fallot Correct answer.
  3. Transposition of the great arteries
  4. Patent ductus arteriosus

Explanation

The four components described - ventricular septal defect, overriding aorta, pulmonary stenosis and right ventricular hypertrophy - constitute the tetralogy of Fallot. Right ventricular outflow obstruction reduces pulmonary flow, producing cyanosis that is unresponsive to oxygen. The classic chest radiograph shows a boot-shaped heart.

Question 47Medical (M.B.B.S./B.D.S./B.H.M.S.) - NEET (UG)-based

Which vitamin deficiency is classically associated with megaloblastic anaemia and subacute combined degeneration of the spinal cord?

  1. Vitamin B1
  2. Vitamin B6
  3. Folate
  4. Vitamin B12 Correct answer.

Explanation

Vitamin B12 is required for methionine synthase activity, and its deficiency causes impaired myelin synthesis leading to posterior column and corticospinal tract damage. It also produces megaloblastic anaemia through the methylfolate trap. Folate deficiency causes megaloblastic anaemia but not neurological degeneration.

Question 48Medical (M.B.B.S./B.D.S./B.H.M.S.) - NEET (UG)-based

A 30-year-old man sustains a midshaft humerus fracture after a fall. Two days later he cannot extend his wrist or fingers and has numbness over the dorsum of the hand between the first and second metacarpals. Which nerve is injured?

  1. Musculocutaneous nerve
  2. Median nerve
  3. Ulnar nerve
  4. Radial nerve Correct answer.

Explanation

The radial nerve runs in the spiral groove against the humeral shaft and is injured in midshaft fractures. It supplies the wrist and finger extensors and the first dorsal web space sensation, giving wrist drop with sensory loss there. The posterior interosseous branch is the usual distal continuation involved.

Question 49Medical (M.B.B.S./B.D.S./B.H.M.S.) - NEET (UG)-based

In the cardiac cycle, which event immediately follows the closure of the atrioventricular valves?

  1. Isovolumetric ventricular relaxation
  2. Isovolumetric ventricular contraction Correct answer.
  3. Ventricular filling
  4. Aortic valve opening

Explanation

Closure of the mitral and tricuspid valves produces the first heart sound and marks the start of ventricular systole. With all valves shut, the ventricles contract without changing volume - isovolumetric contraction. Aortic pressure is then exceeded and the semilunar valves open.

Question 50Medical (M.B.B.S./B.D.S./B.H.M.S.) - NEET (UG)-based

A 45-year-old woman presents with weight gain, cold intolerance, constipation and a diffuse goitre. Serum TSH is elevated and free T4 is low. Which antibody is most characteristically associated with this disorder?

  1. Anti-smooth muscle antibody
  2. Anti-thyroid peroxidase antibody Correct answer.
  3. Anti-double-stranded DNA antibody
  4. Anti-mitochondrial antibody

Explanation

The picture is primary hypothyroidism due to Hashimoto thyroiditis, in which anti-thyroid peroxidase and anti-thyroglobulin antibodies are characteristic. The high TSH with low free T4 confirms a primary thyroid failure rather than a central cause. Lymphocytic infiltration and germinal centres are seen on histology.