110 practice questions on Physics Concepts from the Science & Technology section of the UPSC Prelims syllabus.
110 come with a written explanation and 28 are actual previous year questions.
Try the sample set below - the answer stays hidden until you ask for it.
31 Easy55 Medium24 Hard28 from past papers
Sample questions
Q1
Previous year questionhard
In the context of modern scientific research, consider the following statements about 'IceCube', a particle detector located at South Pole, which was recently in the news :
1. It is the world's largest neutrino detector, encompassing a cubic kilometre of ice.
2. It is a powerful telescope to search for dark matter.
3. It is buried deep in the ice.
Which of the statements given above is/are correct?
A1 only
B2 and 3 only
C1 and 3 only
D1, 2 and 3
Show answer and explanation
Correct answer: D - 1, 2 and 3
All three statements are correct. IceCube, at the Amundsen-Scott South Pole Station, instruments a full cubic kilometre of Antarctic ice with thousands of digital optical modules, making it the largest neutrino detector ever built. Its sensor strings are sunk between roughly 1450 and 2450 metres beneath the surface, so it is literally buried deep in the ice. Beyond detecting astrophysical neutrinos, it also functions as a telescope in the search for dark matter, looking for neutrino signatures that would result from dark matter particle annihilation. Hence 1, 2 and 3.
Q2
Previous year questionmedium
Consider the following pairs:
Objects in space : Description
1. Cepheids : Giant clouds of dust and gas in space
2. Nebulae : Stars which brighten and dim periodically
3. Pulsars : Neutron stars that are formed when massive stars run out of fuel and collapse
How many of the above pairs are correctly matched?
AOnly one
BOnly two
CAll three
DNone
Show answer and explanation
Correct answer: A - Only one
Only one pair is correctly matched, so the answer is Only one. The Pulsars pair is right, as pulsars are rotating neutron stars left behind when massive stars collapse. The first two pairs are swapped, since Cepheids are actually stars that brighten and dim periodically while nebulae are the giant clouds of dust and gas. Because the descriptions for Cepheids and Nebulae are interchanged, only the Pulsars pairing is correct.
Q3
Previous year questionmedium
The efforts to detect the existence of Higgs boson particle have become frequent news in the recent past. What is/are the importance/importances of discovering this particle?
1. It will enable us to understand as to why elementary particles have mass.
2. It will enable us in the near future to develop the technology of transferring matter from one point to another without traversing the physical space between them.
3. It will enable us to create better fuels for nuclear fission.
Select the correct answer using the codes given below.
A1 only
B2 and 3 only
C1 and 3 only
D1, 2 and 3
Show answer and explanation
Correct answer: A - 1 only
The Higgs boson is significant because it is associated with the Higgs field, which explains why elementary particles acquire mass, so statement 1 is correct. Statement 2 describes teleportation of matter, which is science fiction and has nothing to do with the Higgs discovery. Statement 3 about creating better fuels for nuclear fission is also unrelated, since the Higgs concerns fundamental particle physics, not reactor fuel chemistry. Hence only statement 1 is correct.
Q4
Previous year questionhard
Which of the following is/are cited by the scientists as evidence/evidences for the continued expansion of universe?
1. Detection of microwaves in space
2. Observation of redshift phenomenon in space
3. Movement of asteroids in space
4. Occurrence of supernova explosions in space
Select the correct answer using the codes given below:
A1 and 2
B2 only
C1, 3 and 4
DNone of the above can be cited as evidence
Show answer and explanation
Correct answer: A - 1 and 2
Statements 1 and 2 are cited as evidence, so (a) is correct. The redshift of light from distant galaxies, increasing with distance (Hubble's law), is the classic signature that space is expanding. The cosmic microwave background detected in space is the cooled relic radiation of the early universe; its existence and falling temperature are consistent only with a universe that has been expanding since the Big Bang, so it is cited alongside redshift. Statement 3 is wrong because asteroid motion is governed by solar system gravity and says nothing about cosmology. Statement 4 is wrong as supernova explosions by themselves are not the evidence (although distance measurements using Type Ia supernovae later revealed accelerated expansion, the occurrence of explosions is not what is cited).
Q5
Previous year questionmedium
The known forces of nature can be divided into four classes, viz., gravity, electromagnetism, weak nuclear force and strong nuclear force. With reference to them, which one of the following statements is not correct?
AGravity is the strongest of the four
BElectromagnetism acts only on particles with an electric charge
CWeak nuclear force causes radioactivity
DStrong nuclear force holds protons and neutrons inside the nucleus of an atom
Show answer and explanation
Correct answer: A - Gravity is the strongest of the four
The question asks for the incorrect statement. Gravity is actually the weakest of the four fundamental forces, not the strongest, so statement 1 is incorrect and is the answer. The other statements are correct: electromagnetism acts on electrically charged particles, the weak nuclear force is responsible for radioactive (beta) decay, and the strong nuclear force binds protons and neutrons within the nucleus. Hence the not-correct statement is that gravity is the strongest.
Q6
Previous year questionmedium
Ball bearings are used in bicycles, cars, etc., because
Athe actual area of contact between the wheel and axle is increased
Bthe effective area of contact between the wheel and axle is increased
Cthe effective area of contact between the wheel and axle is reduced
DNone of the above statements is correct
Show answer and explanation
Correct answer: C - the effective area of contact between the wheel and axle is reduced
Ball bearings convert sliding friction into rolling friction, which is much smaller. The balls touch the surfaces only at tiny points, so the effective area of contact between the wheel and the axle is greatly reduced, minimizing friction and wear. Increasing either the actual or effective contact area would raise friction, the opposite of what bearings achieve, so options 1 and 2 are wrong. Hence the correct reason is that the effective area of contact is reduced.
Q7
Previous year questionmedium
Organic Light Emitting Diodes (OLEDs) are used to create digital display in many devices. What are the advantages of OLED displays over Liquid Crystal displays?
1. OLED displays can be fabricated on flexible plastic substrates.
2. Roll-up displays embedded in clothing can be made using OLEDs.
3. Transparent displays are possible using OLEDs.
Select the correct answer using the code given below :
A1 and 3 only
B2 only
C1, 2 and 3
DNone of the above statements is correct
Show answer and explanation
Correct answer: C - 1, 2 and 3
OLEDs are self-emissive organic films that need no backlight, which gives all three advantages. They can be deposited on thin flexible plastic substrates (1), enabling roll-up or wearable displays embedded in fabric (2), and they can be made transparent because the emissive layers and electrodes can be largely see-through (3). LCDs, by contrast, require rigid glass and a bulky backlight, so they cannot match these properties. Hence 1, 2 and 3 are all correct.
Q8
Previous year questionmedium
With reference to street-lighting, how do sodium lamps differ from LED lamps?
1. Sodium lamps produce light in 360 degrees but it is not so in the case of LED lamps.
2. As street-lights, sodium lamps have longer life span than LED lamps.
3. The spectrum of visible light from sodium lamps is almost monochromatic while LED lamps offer significant colour advantages in street-lighting.
Select the correct answer using the code given below.
A3 only
B2 only
C1 and 3 only
D1, 2 and 3
Show answer and explanation
Correct answer: C - 1 and 3 only
A sodium lamp's bare bulb radiates light in all directions (about 360 degrees) whereas an LED is directional, so statement 1 is correct. Statement 3 is also correct: low-pressure sodium light is nearly monochromatic yellow, while LEDs can be tuned for far better colour rendering in street lighting. Statement 2 is false because LEDs actually have a much longer service life than sodium lamps, not shorter. Therefore only 1 and 3 are correct, option (c).
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