MCQ
Physics MCQ - Practice Questions with Answers
Solve 5 Physics questions for RAS/RPSC preparation.
Practice questions
Q1Four laboratory placards each pair a mechanical quantity with an SI unit and a dimensional formula: P1. Longitudinal stress — pascal (Pa) — [M L⁻¹ T⁻²] P2. Absolute pressure in a static fluid — pascal (Pa) — [M L T⁻²] P3. Young’s modulus — newton per square metre (N m⁻²) — [M L⁻¹ T⁻²] P4. Surface tension — newton per metre (N m⁻¹) — [M T⁻²] Which placard alone is inconsistent with the defining relation of its quantity?
Longitudinal stress is force per area, so pascal with [M L⁻¹ T⁻²] makes P1 consistent. Young’s modulus equals stress/strain and strain is dimensionless, so P3 correctly repeats those same dimensions with N m⁻². Surface tension is force per length: [M L T⁻²]/[L] = [M T⁻²], so P4 is consistent. Absolute pressure is also force per area and must be [M L⁻¹ T⁻²]; P2 pairs pascal with force’s [M L T⁻²] and is the only inconsistent placard.
Q2In a household wiring and billing discussion, four claims are made: 1. The electricity meter’s commercial monthly reading is recorded in watts, because the meter’s job is to sample the instantaneous power drawn by appliances. 2. The green-insulated earth conductor is bonded to metallic appliance bodies and to a buried metal plate, and in normal healthy operation with no leakage it steadily carries the same load current as the neutral return wire. 3. A fuse made of a low-melting alloy is placed in series with the live path; overloading or short-circuiting causes Joule heating that melts the fuse and opens the circuit. 4. A miniature circuit breaker protects a branch solely by melting a built-in low-melting fusible wire exactly like a rewirable fuse, and therefore cannot be reset after it trips. Which claim is correct?
Claim 1 is false: the commercial bill quantity is energy in kilowatt-hour, not instantaneous power in watts. Claim 2 is false: the green earth wire bonds the metallic body to a buried plate as a low-resistance fault path; it does not steadily carry the ordinary load current like the neutral. Claim 3 is true: a domestic fuse sits in series on the live path and melts by Joule heating when the current becomes unduly high, breaking the circuit. Claim 4 is false: a miniature circuit breaker trips by thermal or magnetic action and can be reset; it is not a one-shot melting fusible wire. Therefore only claim 3 is correct.
Q3An electric iron is marked 1 kW, 220 V. Four workshop conclusions are drawn. Which conclusion alone is scientifically consistent?
Current drawn is P/V = 1000/220 ≈ 4.54 A, so a domestic 5 A fuse belongs in series with the appliance. Separately, the commercial unit of electrical energy is the kilowatt hour, whereas the watt measures power. Taking 0.22 A with a parallel fuse, equating one kilowatt-hour to 1000 J, or rating the fuse in kilowatt each fails either the protection wiring or the energy unit.
Q4Match List-I with List-II and select the option that has only correctly matched pairs. List-I (application / observation) P. Long-distance glass optical-fibre cables carrying light signals Q. Shimmering mirage seen above a hot road surface on a summer afternoon R. Sparkling brilliance of a well-cut diamond S. Light pipe used in medical endoscopy for illuminating internal organs List-II (physical basis) 1. Repeated total internal reflection inside a higher-refractive-index core surrounded by lower-index cladding 2. Total internal reflection linked to refractive-index layering in heated air above the road 3. Total internal reflection favoured by the diamond’s small critical angle 4. Gradual refraction along a continuously varying refractive-index path, without total internal reflection being required Codes:
Optical-fibre cables and endoscopy light pipes both guide light by repeated total internal reflection in a higher-index core clad by a lower-index sheath, so P and S both match 1. A summer road mirage is listed among total-internal-reflection examples arising from heated-air refractive-index layering, so Q matches 2. A cut diamond sparkles largely because its small critical angle supports total internal reflection, so R matches 3. List-II entry 4 is not the working basis of these applications. Therefore only the code P-1, Q-2, R-3, S-1 is fully correct.
Q5A marine-electronics worksheet lists four instrument notes: 1. Depth sounding of submerged objects from a ship is done by launching radar-band electromagnetic microwaves into seawater and timing the echo delay, the same ranging principle used by airborne radar. 2. A moving-coil galvanometer is turned into an ammeter by connecting across its coil a shunt whose resistance is much smaller than the coil resistance, so that most of the circuit current bypasses the coil. 3. The same galvanometer is turned into a voltmeter by connecting in series with its coil a resistance much larger than the coil resistance, so that only a tiny fraction of the circuit current enters the instrument. 4. Current through a chosen circuit element is measured by placing that ammeter arrangement in series with the element, not merely across its terminals in parallel. Which of the notes given above is/are NOT correct?
Note 1 is false: ship-borne depth sounding uses ultrasonic sound pulses in water; radar-band electromagnetic microwaves are for ranging in air and are strongly attenuated in seawater. Note 2 is true: a shunt of much smaller resistance in parallel converts a moving-coil galvanometer into an ammeter. Note 3 is true: a much larger series resistance converts it into a voltmeter. Note 4 is true: an ammeter must sit in series with the element whose current is measured. Therefore only note 1 is not correct.
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