← MES Jr. Grade
Past Questions
Two electric dipoles aligned paralleled to each other and having the same axis exert a force F on each other, when a distance d apart. If the dipoles are at distance 2d apart, then the mutual force between them would be
A)
F/2
B)
F/4
C)
F/8
D)
F/16
For two electric dipoles aligned parallel to each other with the same axis, the mutual force varies inversely as the fourth power of the separation distance: F ∝ 1/r^4. Therefore, if the distance is increased from d to 2d, the force becomes F' = F/(2^4) = F/16. Hence option d is correct.
Why the others are incorrect:
- a) F/2 would correspond to a much weaker distance dependence, not the dipole-dipole law.
- b) F/4 is the scaling for an inverse-square law, which applies to point charges, not dipoles.
- c) F/8 would correspond to an inverse-cube type dependence, still not correct for dipole-dipole force.
So the correct answer is d) F/16.
Ceramic loses its insulating properties above a temperature called
A)
melting point
B)
solidification point
C)
curie point
D)
flash point
Ceramic materials used as electrical insulators can lose their insulating behavior above the Curie point, because at this temperature certain ferroelectric ceramics undergo a phase change and their dielectric properties drop sharply. Hence, the correct answer is Curie point. Solidification point is the temperature at which a liquid turns into a solid, which is unrelated to insulation. Flash point is the temperature at which a material gives off enough vapor to ignite, also unrelated. Melting point is the temperature at which a solid becomes liquid; while ceramics may fail at high temperatures, the specific loss of insulating properties referred to here is associated with the Curie point.
Essential requirement of an electrical measuring instrument is that
A)
Its resistance should be low
B)
It is always connected in series in the circuit
C)
Its introduction into the circuit under measurement does not alter the circuit conditions and the power consumed by it for its operation is small
D)
Its resistance should be infinite
An electrical measuring instrument should measure the quantity without significantly disturbing the circuit. Hence, its introduction into the circuit must not alter the circuit conditions, and it should consume very little power for its own operation. This is the essential requirement of a good measuring instrument.
Why the other options are incorrect:
- a) "Its resistance should be low" is not generally true for all instruments. For example, voltmeters should have very high resistance, while ammeters should have very low resistance.
- b) "It is always connected in series in the circuit" is false. Ammeters are connected in series, but voltmeters are connected in parallel.
- d) "Its resistance should be infinite" is incorrect as a general statement. Infinite resistance is desirable for an ideal voltmeter, not for all electrical measuring instruments.
A battery charger can drive a current of 5A into a 1 ohm resistance connected at its output terminals. If it is able to charge an ideal 2 V battery at 7 A rate, then its Thevenin’s equivalent will be
A)
7.5 V in series with 0.5 ohm
B)
12.5 V in series with 1.5 ohm
C)
7.5 V in parallel with 0.5 ohm
D)
12.5 V in parallel with 1.5 ohm
Let the charger be replaced by its Thevenin equivalent: a source Vth in series with Rth.
1) With a 1 ohm load, it delivers 5 A.
So the terminal voltage is V = IR = 5 × 1 = 5 V.
Hence, Vth - 5Rth = 5. ...(1)
2) It can charge an ideal 2 V battery at 7 A.
For charging, the charger terminal voltage must be 2 V + 7Rth.
So Vth - 7Rth = 2. ...(2)
Subtract (2) from (1):
(Vth - 5Rth) - (Vth - 7Rth) = 5 - 2
2Rth = 3
Rth = 1.5 ohm
Substitute in (1):
Vth - 5(1.5) = 5
Vth = 12.5 V
Therefore, the Thevenin equivalent is 12.5 V in series with 1.5 ohm.
Why others are wrong:
- a and c have incorrect values of both source voltage and resistance.
- d is wrong because Thevenin equivalent is a voltage source in series with resistance, not in parallel (that would be Norton form).
In the semiconductor, the movement of holes is due to
A)
movement of holes in the conduction band
B)
movement of electrons in conduction band
C)
movement of electrons in valence band
D)
movement of holes in valence band
In a semiconductor, a hole is the absence of an electron in the valence band. When neighboring valence electrons move to fill this vacancy, the vacancy appears to move in the opposite direction. Thus, hole conduction is effectively due to the movement of holes in the valence band. Option d is correct.
Why the others are incorrect:
- a) Holes do not exist in the conduction band; conduction band transport is mainly by electrons.
- b) Movement of electrons in the conduction band explains electron conduction, not hole conduction.
- c) Electrons in the valence band are generally bound; their movement does not represent hole conduction directly. Hole motion is the effective motion of vacancies in the valence band.
The ratio of tangential component of electric field at the surface of a conductor and the linear current density which flows as a result of this field is
A)
characteristic impedance
B)
surface impedance
C)
critical impedance
D)
electromagnetic link impedance
The ratio of the tangential electric field at the surface of a conductor to the surface current density (linear current density) produced by it is called the **surface impedance**. It is defined as Zs = Et / Js, where Et is the tangential electric field and Js is the current density on the conductor surface.
Why the others are incorrect:
- **Characteristic impedance**: This is the voltage-to-current ratio of a transmission line for a traveling wave, not a conductor surface property.
- **Electromagnetic link impedance**: Not the standard term for the ratio given in the question.
- **Critical impedance**: This is not the correct electromagnetic term for this definition.
What type of bridge circuit is used to measure inductance and capacitance?
A)
Wheatstone bridge
B)
D-C bridge
C)
A-C bridge
D)
A-C, D-C bridge
AC bridges are used to measure inductance and capacitance because these quantities are associated with alternating-current impedance and phase relationships. Examples include Maxwell, Hay, Schering, and Anderson bridges. A DC bridge such as the Wheatstone bridge is used for resistance measurement only, not for inductance or capacitance. Therefore, the correct option is AC bridge. The option 'A-C, D-C bridge' is incorrect because DC bridges do not directly measure inductance or capacitance.
The dynamic characteristics of capacitive transducer are similar to those of
A)
Low pass filters
B)
High pass filters
C)
Notch filters
D)
Band stop filters
A capacitive transducer behaves like a low-pass system in its dynamic response: it can follow slow changes in the measurand well, but its output cannot respond effectively to very rapid variations because of the RC time constant and associated circuit limitations. Hence, its dynamic characteristics are similar to those of a low-pass filter.
Why others are incorrect:
- b) High-pass filters: these pass rapid changes and block steady/slow signals, which is opposite to the usual capacitive transducer behavior.
- c) Notch filters: these reject a narrow band of frequencies; this does not describe capacitive transducer dynamics.
- d) Band-stop filters: these suppress a range of frequencies, which is also not the typical response characteristic of a capacitive transducer.
Hall’s effect can be used to measure
A)
electric field intensity
B)
magnetic field intensity
C)
carrier concentration
D)
permeability
Hall’s effect is the development of a transverse Hall voltage when a current-carrying conductor or semiconductor is placed in a magnetic field. Since the Hall voltage is directly related to the magnetic flux density, the effect is used to measure magnetic field intensity. Option (b) is therefore correct. Option (a) is incorrect because Hall effect does not directly measure electric field intensity. Option (c) is incorrect because carrier concentration can be determined indirectly from Hall measurements, but it is not the primary quantity asked here. Option (d) is incorrect because permeability is not measured by Hall effect.
A conductor of length 1 m moves at right angles to a magnetic field of flux density 1 Wb/m2 with a velocity of 20 m/s. The induced emf in conductor will be
A)
100 V
B)
20 V
C)
2 V
D)
40 V
For a conductor moving perpendicular to a magnetic field, the induced emf is given by e = B l v. Here B = 1 Wb/m^2 (1 T), l = 1 m, and v = 20 m/s. So, e = 1 × 1 × 20 = 20 V. Therefore, option (b) is correct. Option (a) 100 V is too high, option (d) 40 V is double the correct value, and option (c) 2 V is too low.
Frequency can be measured by using
A)
Maxwell’s bridge
B)
Schering bridge
C)
Heaviside Campbell bridge
D)
Wien’s bridge
Wien’s bridge is used for frequency measurement because it is a frequency-sensitive AC bridge whose balance condition depends on the supply frequency. By adjusting the bridge to null, the unknown frequency can be determined from the bridge components. Maxwell’s bridge is mainly used to measure inductance, Schering bridge is used to measure capacitance and dielectric loss, and Heaviside-Campbell bridge is used for measuring self-inductance of coils, not frequency.
Two incandescent light bulbs of 40 W and 60 W rating are connected in series across the mains. Then
A)
bulbs together consume 100 W
B)
bulbs together consume 50 W
C)
60 W bulb glows brighter
D)
40 W bulb glows brighter
For incandescent bulbs, resistance is approximately R = V^2/P at rated voltage. So the 40 W bulb has higher resistance than the 60 W bulb. When connected in series, the same current flows through both bulbs, and power dissipated in each is P = I^2R. Therefore the bulb with larger resistance, i.e. the 40 W bulb, dissipates more power and glows brighter. The 60 W bulb glows dimmer.
Why the other options are wrong:
- (c) 60 W bulb glows brighter: incorrect because in series the same current flows, so the higher-resistance 40 W bulb gets more power.
- (b) bulbs together consume 50 W: incorrect; the total power depends on the series current and the combined resistance, not simply the arithmetic mean of ratings.
- (a) bulbs together consume 100 W: incorrect; in series across mains, the total power is much less than the sum of their individual rated powers because each bulb operates below its rated voltage.
A transducer converts
A)
mechanical energy into electrical energy
B)
mechanical displacement into electrical signal
C)
one form of energy into another form of energy
D)
electrical energy into mechanical form
A transducer is a device that converts energy from one form into another form. This is the general definition, so option (c) is correct. Option (b) is too specific because only some transducers convert mechanical displacement into an electrical signal (e.g., LVDT, strain gauge). Option (a) describes a specific type of transducer such as a generator, which converts mechanical energy to electrical energy. Option (d) describes an actuator or motor, which converts electrical energy into mechanical form, not the general meaning of a transducer.
A series RLC circuit consisting of R=10 ohms, XL = 20 ohms and XC = 20 ohms is connected across an AC supply of 100 V (rms). The magnitude and phase angle (with reference to supply voltage) of the voltage across the inductive coil are respectively
A)
100 V, 90o
B)
100 V, -90o
C)
200 V, 90o
D)
200 V, -90o
In a series RLC circuit, the net reactance is X = XL - XC = 20 - 20 = 0, so the circuit is at resonance. Hence the total impedance is purely resistive: Z = R = 10 ohms. Therefore the circuit current is I = V/Z = 100/10 = 10 A.
The voltage across the inductive coil is VL = I XL = 10 × 20 = 200 V. In a pure inductor, voltage leads current by 90°, and since the supply voltage is in phase with the current at resonance, the inductor voltage is 90° ahead of the supply voltage.
So the correct answer is 200 V, 90°.
Why others are wrong:
- b) 100 V, -90°: wrong magnitude and wrong phase.
- c) 200 V, -90°: correct magnitude but wrong phase sign; inductor voltage leads, not lags.
- d) 200 V, -90°: same issue as c, and not the correct phase relation.
Which one following statements does not pertain to the equation div B = 0?
A)
magnetic field is perpendicular to the electric field
B)
there are no sinks and sources for magnetic fields
C)
single magnetic pole cannot exist
D)
B is solenoidal
The equation div B = 0 is Gauss’s law for magnetism. It means the magnetic field has zero divergence, so magnetic field lines do not begin or end anywhere. Hence, B is solenoidal (d), there are no sinks or sources for magnetic fields (b), and a single magnetic pole cannot exist (c) because isolated magnetic monopoles are not observed in classical electromagnetism. Option (a) does not follow from div B = 0: the statement that magnetic field is perpendicular to the electric field is unrelated to the divergence of B. That is not a consequence of Gauss’s law for magnetism.
Which of the following devices can not be used to measure pressure?
A)
LVDT
B)
Strain gauge
C)
Pyrometer
D)
Pirani gauge
Pyrometer is the correct answer because it is an instrument used to measure high temperature, not pressure. Therefore, it cannot be used for pressure measurement.
Why the others are incorrect:
- Strain gauge: Can be used in pressure transducers; pressure causes strain in an elastic element, which the gauge measures.
- LVDT: Can be used in pressure measurement indirectly in pressure transducers by sensing displacement of a diaphragm or piston caused by pressure.
- Pirani gauge: Is a vacuum pressure gauge used to measure low pressures by thermal conductivity changes of a gas.
Potential energy we stored in a system of ‘n’ point charge equals
A)
sum(V_i)
B)
sum(V_i^2)
C)
sum(V_i^2)
D)
sum(V_i)
For a system of point charges, the electrostatic potential energy is the work required to assemble the charges from infinity. It is given by U = (1/2)\sum_i q_i V_i, where V_i is the potential at the location of the i-th charge due to all the other charges (the factor 1/2 avoids double counting). Since the question’s options only list forms involving sums of V_i or V_i^2, the correct intended choice is the linear sum, i.e. \u03a3V_i, not the square.
Why the others are incorrect:
- \u03a3(V_i^2): potential energy is not proportional to the square of potential in this context.
- The duplicate option with \u03a3(V_i^2) is also incorrect for the same reason.
- \u03a3(V_i) is the only option matching the linear dependence expected in the standard expression (up to the missing charge factor and 1/2 in the question).
In practice, Earth is chosen as a place of zero electric potential because it
A)
is non-conducting
B)
is easily available
C)
keep loosing and gaining electric charge every day
D)
has almost constant potential
Earth is taken as zero potential because it is so large that it can absorb or supply charge without any appreciable change in its potential. Hence its potential remains practically constant, making it a convenient reference level. Option (a) is wrong because Earth is not non-conducting; it is a conductor. Option (b) is not the physical reason, though Earth is indeed easily available. Option (c) is incorrect because the statement about daily losing and gaining charge is not the basis for choosing Earth as zero potential.
Electrical conductivity of copper reduces with addition of a small amount of nickel because
A)
The mobility decreases due to creation of new scattering centers for electrons
B)
Nickel is ferromagnetic
C)
Less free electrons are available for conduction
D)
The electrons of copper become bound to nickel atoms and are not free to move
Adding a small amount of nickel to copper forms an alloy in which nickel atoms act as impurity/scattering centers. These disturb the regular crystal lattice and increase electron scattering, so the mobility of conduction electrons decreases and electrical conductivity falls.
Why others are incorrect:
- b: Ferromagnetism of nickel is not the reason for reduced conductivity in copper.
- c: The number of free electrons in copper does not significantly decrease; conductivity mainly drops due to reduced mobility, not fewer carriers.
- d: Copper electrons do not become permanently bound to nickel atoms; the main effect is scattering, not electron capture.
The minimum error distribution in the period of software development is in
A)
requirement analysis
B)
design phase
C)
coding
D)
testing
Based on established principles in Computer Science & Engineering, the correct and most appropriate choice is 'coding' (Option C).
Which of the following commands is used to delete all rows and free up space from a table?
A)
Drop
B)
Delete
C)
Truncate
D)
Alter
Based on established principles in Computer Science & Engineering, the correct and most appropriate choice is 'Truncate' (Option C).
__________ function is used to find the number of values in a column.
A)
SUM
B)
COUNT
C)
ADD
D)
AVG
Based on established principles in Computer Science & Engineering, the correct and most appropriate choice is 'COUNT' (Option B).
The most important feature of spiral model is
A)
requirement analysis.
B)
risk management.
C)
quality management.
D)
configuration management.
Based on established principles in Computer Science & Engineering, the correct and most appropriate choice is 'risk management.' (Option B).
ER Diagram represents a overall __________ of a Database graphically.
A)
Physical Structure
B)
Logical Structure
C)
Domain Structure
D)
Architectural Representation
Based on established principles in Computer Science & Engineering, the correct and most appropriate choice is 'Logical Structure' (Option B).
Statistical software quality assurance in software engineering involves
A)
using sampling in place of exhaustive testing of software.
B)
surveying customers to find out their opinions about product quality.
C)
tracing each defect to its underlying cause, isolating the vital few causes, and moving to correct them.
D)
tracing each defect to its underlying causes, and using the Pareto principle to correct each problem found.
Based on established principles in Computer Science & Engineering, the correct and most appropriate choice is 'tracing each defect to its underlying causes, and using the Pareto principle to correct each problem found.' (Option D).