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Past Questions — 2026
Define natural response of a circuit and explain with RL example.
Explain magnetization and classify magnetic materials.
The equivalent resistance between two nodes of a circuit can be most easily determined using:
A)
Mesh analysis
B)
Nodal analysis
C)
Superposition theorem
D)
Maximum power transfer theorem
The equivalent resistance between two nodes is most easily found by applying a test source and using nodal analysis. In nodal analysis, the current-voltage relations at nodes make it straightforward to compute the voltage-to-current ratio, i.e., the equivalent resistance. Mesh analysis can also be used in some cases, but it is generally less direct for finding resistance between two nodes. Superposition theorem is for analyzing circuits with multiple sources, and maximum power transfer theorem is unrelated to equivalent resistance determination.
The intrinsic impedance of free space is approximately:
A)
50 Ω
B)
100 Ω
C)
377 Ω
D)
500 Ω
The intrinsic impedance of free space is given by η₀ = √(μ₀/ε₀), where μ₀ is the permeability of free space and ε₀ is the permittivity of free space. Substituting the standard values gives η₀ ≈ 376.7 Ω, which is approximately 377 Ω. Hence, option (c) is correct. The other values are far from the standard intrinsic impedance of free space.
Induction type single phase energy meters measure electric energy in:
A)
kW
B)
Wh
C)
kWh
D)
None of the above
An induction type single-phase energy meter measures electrical energy consumed over time, which is expressed in kilowatt-hour (kWh). It does not measure instantaneous power in kW, and Wh is a smaller unit but the standard billing unit is kWh. Hence, the correct answer is kWh.
A network with no energy storage elements exhibits:
A)
Transient response
B)
Steady-state response only
C)
Oscillatory response
D)
Resonant response
A network with no energy storage elements means it has only resistive elements, with no inductors or capacitors. Since transient behavior arises due to energy storage in L and C, such a network cannot exhibit transient response. Therefore, it shows only steady-state response. Options (a), (c), and (d) require reactive elements, so they are incorrect.
A 50 Hz RLC circuit has, L = 0.2 H, C = 100 μF. The resonance frequency is approximately:
A)
35 Hz
B)
50 Hz
C)
70 Hz
D)
100 Hz
For a resonant RLC circuit, the resonance frequency is
f0 = 1 / (2π√(LC))
Given:
L = 0.2 H
C = 100 μF = 100 × 10^-6 F = 10^-4 F
So,
LC = 0.2 × 10^-4 = 2 × 10^-5
√(LC) ≈ √(2 × 10^-5) ≈ 4.47 × 10^-3
Therefore,
f0 ≈ 1 / (2π × 4.47 × 10^-3) ≈ 35.6 Hz
So the nearest option is 35 Hz.
The other options are not close to the calculated resonance frequency.
The household energy meter is:
A)
an indicating instrument
B)
a recording instrument
C)
an integrating instrument
D)
none of the above
A household energy meter measures the total electrical energy consumed over time in kWh. Instruments that measure the total quantity over a period are called integrating instruments. An indicating instrument shows the instantaneous value, and a recording instrument continuously records the variation with time. Therefore, the correct answer is an integrating instrument.
At resonance in a series RLC circuit, impedance is:
A)
Minimum
B)
Maximum
C)
Zero
D)
Infinite
In a series RLC circuit at resonance, the inductive reactance equals the capacitive reactance (XL = XC). These cancel each other, so the circuit impedance becomes only the resistance R, which is the smallest possible value for that circuit. Hence, impedance is minimum. It is not zero because resistance remains present, and it is not maximum or infinite in a series circuit at resonance.
Kelvin double bridge is used for measuring:
A)
High resistance
B)
Low resistance
C)
Medium resistance
D)
Insulation resistance
A Kelvin double bridge is designed to measure very low resistances accurately. It eliminates the effect of lead and contact resistances, which become significant when the resistance under test is small. Therefore, it is used for measuring low resistance. High resistance is measured by other methods such as a megohmmeter or loss of insulation methods, and medium resistance is generally measured by Wheatstone bridge-type arrangements.
Hall effect is used to determine:
A)
Carrier concentration
B)
Carrier mobility
C)
Type of semiconductor
D)
All of these
The Hall effect is used to find several key semiconductor parameters: (1) the sign of Hall coefficient tells the type of semiconductor (n-type or p-type), (2) the Hall coefficient helps determine carrier concentration, and (3) combining Hall coefficient with conductivity gives carrier mobility. Therefore, all the listed options are correct.
Magnetic permeability indicates:
A)
Electrical resistance
B)
Ability to conduct electricity
C)
Ability to support magnetic field
D)
Thermal conductivity
Magnetic permeability is a measure of how easily a material can support or allow the formation of a magnetic field within it. A higher permeability means the material is more easily magnetized. The other options are unrelated: electrical resistance is opposition to electric current, ability to conduct electricity refers to electrical conductivity, and thermal conductivity is about heat transfer.
Strain gauge transducers are used to measure:
A)
Pressure and force
B)
Temperature
C)
Light intensity
D)
Magnetic field
A strain gauge measures strain, i.e., the deformation of a body under load. Since strain is produced by applied force, strain gauge transducers are commonly used in devices like load cells and pressure sensors to measure force and pressure. Temperature, light intensity, and magnetic field are measured by different types of transducers, not strain gauges.
Network synthesis is the process of:
A)
Simplifying circuits
B)
Designing networks from transfer function
C)
Measuring voltage
D)
Measuring current
Network synthesis means constructing or designing an electrical network that realizes a given desired function, usually a transfer function, impedance, admittance, or system response. It is not about simply simplifying circuits, and it is unrelated to measuring voltage or current. Therefore, the correct option is (b).
Hysteresis loss is undesirable in:
A)
Permanent magnets
B)
Transformer cores
C)
Recording tapes
D)
Magnetic switches
Hysteresis loss occurs when a magnetic material is repeatedly magnetized and demagnetized. This loss is undesirable in transformer cores because transformers work with alternating magnetic flux, so repeated cycling causes energy loss as heat and reduces efficiency. In contrast, permanent magnets need materials with high hysteresis, recording tapes rely on magnetic properties for storing data, and magnetic switches are not primarily affected in the same way as transformer cores.
The SI unit of electric flux density D is:
A)
V/m
B)
C/m²
C)
Wb/m²
D)
A/m
Electric flux density D is also called electric displacement. From Gauss’s law, D = Q/A, so its SI unit is coulomb per square metre (C/m²). Option (a) V/m is the unit of electric field, (c) Wb/m² is magnetic flux density, and (d) A/m is the unit of magnetic field intensity.
Data acquisition system mainly consists of:
A)
Sensors
B)
Signal conditioning
C)
ADC and processor
D)
All of the above
A data acquisition (DAQ) system generally includes sensors to measure physical quantities, signal conditioning circuits to prepare the signal for processing, and an ADC (analog-to-digital converter) with a processor/computer to convert, process, and store the data. Since all three are essential parts of a typical DAQ system, the correct answer is All of the above.
Ferrites are commonly used in:
A)
High-frequency transformers
B)
Electric heaters
C)
DC generators
D)
Lamps
Ferrites are magnetic ceramic materials with high electrical resistivity and low eddy current losses, so they work well at high frequencies. That is why they are commonly used in high-frequency transformers and inductors. Electric heaters, DC generators, and lamps are not typical applications of ferrites.
The curl of magnetic field equals:
A)
∂B/∂t
B)
J + ∂D/∂t
C)
∇·E
D)
∇·D
This is Ampere-Maxwell law in differential form: ∇ × B = μ₀J + μ₀ε₀(∂E/∂t), or equivalently ∇ × H = J + ∂D/∂t. Among the given options, the expression matching the curl relation for magnetic field is J + ∂D/∂t. Option (a) is related to Faraday’s law, while (c) and (d) are divergence relations, not curl relations.
A frequency counter counts 5000 pulses in 0.1 s. The frequency of the signal is:
A)
5 kHz
B)
10 kHz
C)
50 kHz
D)
500 kHz
Frequency is the number of pulses per second. Here, 5000 pulses are counted in 0.1 s, so frequency = 5000 / 0.1 = 50000 Hz = 50 kHz. Therefore, the correct option is (c).
Which of the following is a ferromagnetic material?
A)
Copper
B)
Aluminium
C)
Iron
D)
Silver
Ferromagnetic materials are strongly attracted by magnetic fields and can be permanently magnetized. Iron is a classic ferromagnetic material. Copper, aluminium, and silver are not ferromagnetic: copper and silver are diamagnetic, while aluminium is paramagnetic.
Define transducers and explain working of resistive transducers with examples.
State Maximum Power Transfer theorem and derive its condition.
A wire of length 1m has a resistance of 2Ω. What is the resistance of the second wire, whose specific resistance is double that of the first, if the length of wire is 3m and the diameter is double that of the first?
Find the current supplied by the battery for the figure shown in the paper.