General Science PYQ – Electricity, Magnetism and Electronics | Online Quiz

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General Science PYQ – Electricity, Magnetism and Electronics – 29 questions, subject: Science. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

Junior Analyst 2023

The unit of electric current is ______

Correct Answer: D [ampere]

Explanation:

The SI unit of electric current is the ampere (A), one of the seven base units, equal to one coulomb of charge per second.

Hostel Supdt. cum PTO 2024

The SI unit of electric potential (or) potential difference is

Correct Answer: C [volt]

Explanation:

Potential difference is work done per unit charge (V = W/q), so its SI unit joule per coulomb is the volt.

Group 2/2A 2024

A current of 0.5 A passes through a lamp for two minutes; then the number of electrons that pass through the lamp is

Correct Answer: D [3.8 × 10²⁰ electrons]

Explanation:

Charge Q = It = 0.5 x 120 = 60 C, and dividing by the electron charge 1.6 x 10^-19 C gives about 3.8 x 10^20 electrons.

Executive Officer Gr. III (HR&CE) 2022

The force of attraction between two charges at distance 'd' is 'F'. What distance apart should these charges be kept in the same medium, so that the force becomes 16F?

Correct Answer: B [d/4]

Explanation:

By Coulomb's law F is proportional to 1/d squared, so for the force to become 16 times larger the distance must be reduced to d/4.

Group 1 2024

The work done in moving a positive charge on an equipotential surface is
(i) Finite
(ii) Positive
(iii) Negative
(iv) Zero

Correct Answer: B [(iv) only]

Explanation:

All points on an equipotential surface have the same potential, so the potential difference is zero and the work done (W = qdV) in moving a charge on it is zero.

CTS (Non-Interview Posts) 2024

An electric frying pan draws 12 A current when connected to a 120 V circuit. Then, the electric resistance of the frying pan is

Correct Answer: A [10 ohm]

Explanation:

By Ohm's law, resistance R = V/I = 120/12 = 10 ohm.

CTS (ITI Posts) 2024

Calculate the equivalent resistance between A and B in the given circuit: three pairs of resistors in series – (2 Ω ∥ 2 Ω), (4 Ω ∥ 4 Ω), (6 Ω ∥ 6 Ω).

Correct Answer: C [6 Ω]

Explanation:

Each parallel pair of equal resistors gives half the value (1, 2 and 3 ohm), and these in series add up to 6 ohm.

ARGS 2020

Two capacitors of capacitance 3 μF and 6 μF are connected in series combination. Their equivalent capacitance will be

Correct Answer: A [2 μF]

Explanation:

For capacitors in series 1/C = 1/3 + 1/6 = 1/2, so the equivalent capacitance is 2 microfarad.

Road Inspector 2023

An electric heater of resistance 5 Ω is connected to an electric source. If a current of 6 A flows through the heater, then find the amount of heat produced in 5 minutes.

Correct Answer: C [54000 J]

Explanation:

By Joule's law, heat H = I squared x R x t = 36 x 5 x 300 = 54,000 J.

10.

Combined Engineering Subordinate Service 2023

The metal/metals which excel in the conduction of heat and electricity

Correct Answer: B [Copper and Silver]

Explanation:

Silver is the best conductor of heat and electricity, followed by copper, which is used in wires because silver is costly.

11.

Group 1B/1C 2024

Electrical wire is enclosed/covered with a layer of plastic material to make it

Correct Answer: C [Safe]

Explanation:

Plastic is an insulator, so covering wires with it makes them safe by preventing electric shock and short circuits.

12.

Group 4 2022

Correctly match the component and its use in a circuit:
(a) Galvanometer – 1. Used to fix the magnitude of the current through a circuit
(b) Voltmeter – 2. Used to measure current
(c) Ammeter – 3. Used to measure potential difference
(d) Resistor – 4. Used to detect the current and its direction

Correct Answer: A [4 3 2 1]

Explanation:

A galvanometer detects current and its direction, a voltmeter measures potential difference, an ammeter measures current and a rheostat regulates it, giving 4 3 2 1.

13.

Fisheries Inspector / SI 2023

Application of Cathode Ray Oscillograph (CRO) is

Correct Answer: D [All the above]

Explanation:

A cathode ray oscillograph displays AC voltage waveforms, sound waveforms from instruments and small AC and DC potentials, so all the uses are correct.

14.

District Child Protection Officer 2022

Alternating current is converted into direct current by

Correct Answer: B [Rectifier]

Explanation:

A rectifier uses diodes to convert alternating current into direct current, whereas a dynamo makes electricity and a transformer changes AC voltage.

15.

Group 1 2024

The principle of transformer is

Correct Answer: B [Mutual induction]

Explanation:

A transformer works on mutual induction: a changing current in the primary coil induces an emf in the secondary coil.

16.

Asst. Public Prosecutor Gr. II 2025

Assertion: Lenz's law violates the principle of conservation of energy.
Reason: Induced emf always opposes the change in magnetic flux responsible for its production.

Correct Answer: D [Assertion is false and the reason is true]

Explanation:

Lenz's law is based on conservation of energy because the induced emf opposes the flux change, so the assertion is false while the reason is true.

17.

GSCE 2021

Velocity of electromagnetic waves C is equal to

Correct Answer: C [1/√(μ₀ε₀)]

Explanation:

From Maxwell's theory, the speed of electromagnetic waves in vacuum is c = 1/sqrt(mu0 x epsilon0), about 3 x 10^8 m/s.

18.

Group 2/2A 2025

Which of the following statements are true? Essential properties of magnetic materials to be used as an electromagnet:
I. Narrow hysteresis loop
II. High permeability
III. High coercivity
IV. Low retentivity

Correct Answer: D [I, II and IV are correct]

Explanation:

An electromagnet's core must lose magnetism when current stops, so it needs narrow hysteresis loop, high permeability, low retentivity and low coercivity, making I, II and IV correct.

19.

CTS (ITI Posts) 2025

Assertion [A]: Ferromagnetic substances can be permanently magnetised.
Reason [R]: Ferromagnetic materials have strong atomic magnetic dipoles that align in the presence of an external magnetic field, leading to permanent magnetisation.

Correct Answer: A [Both [A] and [R] are true and [R] is the correct explanation of [A]]

Explanation:

Ferromagnetic substances have strong atomic dipoles that form domains and stay aligned in one direction, so they can be permanently magnetised and the reason explains the assertion.

20.

Fisheries Inspector / SI 2023

The converse of magnetostriction effect is

Correct Answer: B [Villari effect]

Explanation:

The change in dimensions of a material on magnetisation is magnetostriction, and its converse, change in magnetisation under mechanical stress, is the Villari effect.

21.

Fisheries Inspector / SI 2023

In Magnetic Resonance Imaging (MRI), ______ wire is used to produce strong magnetic field.

Correct Answer: C [Superconducting]

Explanation:

MRI uses superconducting wire coils because their zero resistance lets very large currents flow without energy loss, producing a strong, stable magnetic field.

22.

AD Town & Country Planning 2022

The transition between normal and superconducting state is thermodynamically

Correct Answer: D [Reversible]

Explanation:

The change between normal and superconducting states occurs on cooling below or heating above the critical temperature and is thermodynamically reversible.

23.

CTS (Interview Posts) 2024

The effect of temperature on electronic and ionic polarisabilities is

Correct Answer: D [Independent of temperature]

Explanation:

Electronic and ionic polarisabilities arise from displacement of electrons or ions and are independent of temperature, unlike orientational polarisation.

24.

Group 1 2022

Which one of the statements is correct for Li-ion batteries?

Correct Answer: A [While the battery is discharging, the anode releases lithium ions to the cathode]

Explanation:

In a Li-ion battery, lithium ions move from the anode to the cathode during discharge and in the reverse direction during charging.

25.

EO Group VII (HR&CE) 2022

In TV transmission the audio signal is ______ modulated.

Correct Answer: D [Frequency]

Explanation:

In television transmission the picture signal is amplitude modulated while the audio signal is frequency modulated because FM is less affected by noise.

26.

Mass Interviewer 2023

______ and ______ bands are used for transmission of TV programmes.

Correct Answer: D [VHF, UHF]

Explanation:

Television programmes are broadcast in the VHF (30-300 MHz) and UHF (300 MHz-3 GHz) bands.

27.

Asst. Conservator of Forests 2023

Which of the following are correct? The conditions at which an amplifier behaves as an oscillator are
(i) Amplifier should have a positive feedback
(ii) Aβ = 1
(iii) Aβ = 0
(iv) Amplifier should have a negative feedback

Correct Answer: A [(i) and (ii) are correct]

Explanation:

An amplifier acts as an oscillator when it has positive feedback and the loop gain A-beta equals 1 (Barkhausen condition).

28.

AHGS 2021

The Boolean expression for XOR gate is

Correct Answer: A [A·B′ + A′·B]

Explanation:

The XOR gate gives output 1 only when the inputs differ, so its Boolean expression is Y = A.B' + A'.B.

29.

ADGS 2021

An AND gate can be obtained by repetitive use of

Correct Answer: D [Both (B) and (C)]

Explanation:

NAND and NOR are universal gates, so an AND gate can be built by repeated use of either of them.

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