Physics GK Quiz-1

Physics GK Quiz-1

Physics Multiple Choice Questions (MCQs) Quiz for State and UPSC Civil Services Examinations. Objective Questions on Physics for competitive examinations.

    1. For which Diode is used ?

    (1) modulation
    (2) oscillation
    (3) amplification
    (4) purification
    Answer:
    1. (4) The most common function of a diode is to allow an electric current to pass in one direction (called the diode’s forward direction), while blocking current in the opposite direction (the reverse
    direction).This unidirectional behavior is called rectification or verification and is used to convert alternating current to direct current, including extraction of modulation from radio signals in radio receivers— these diodes are forms of rectifiers diode is a twoterminal electronic component with an asymmetric transfer characteristic, with low (ideally zero) resistance to current flow in one direction, and high (ideally infinite) resistance in the other.

    2. Who among the following developed the technology of underground nuclear explosion ?

    (1) Dr. Homi J. Bhabha
    (2) Dr. Vikram Sarabhai
    (3) Dr. Raja Ramanna
    (4) Dr. P. K. Iyengar
    Answer:
    2. (1) Homi Jehangir Bhabha was an Indian nuclear physicist, founding director, and professor of physics at the Tata Institute of Fundamental Research. Colloquially known as “father of Indian nuclear
    programme,” Bhabha gained international prominence after deriving a correct expression for the probability of scattering positrons by electrons, a process now known as Bhabha scattering. His major contribution included his work on Compton scattering, R-process, and furthermore the advancement of nuclear physics. He was awarded Padma Bhushan by Government of India in 1954.

    3. Which among the following types of coal produces most heat per unit ?

    (1) Coal 
    (2) Lignite
    (3) Anthracite 
    (4) Pit
    Answer:
    3. (3) The heat content of anthracite ranges from 22 to 28 million Btu per short ton (26 to 33 MJ/kg) on a moist, mineral-matter-free basis. Anthracite (“coallike”) is a hard, compact variety of mineral coal that has a high luster. It has the highest carbon content, the fewest impurities, and the highest calorific content of all types of coals, which also include bituminous coal and lignite. Anthracite is the most metamorphosed type of coal (but still represents low-grade metamorphism), in which the carbon content is between 92.1% and 98%.

    4. Which among the following waves is used for communication by artificial satellites ?

    (1) Micro waves
    (2) Radio waves
    (3) A. M.
    (4) Frequency of 1016 series
    Answer:
    4. (1) For fixed (point-to-point) services, communications satellites provide a microwave radio relay technology complementary to that of communication cables. They are also used for mobile applications such as communications to ships, vehicles, planes and handheld terminals, and for TV and radio broadcasting. Microwave technology is extensively used for pointto-point telecommunications (i.e., non broadcast uses). Microwaves are especially suitable for this use since they are more easily focused into narrow beams than radio waves, and also their comparatively higher frequencies allow broad bandwidth and high data flow.

    5. What is found in frequency modulation ?

    (1) Fixed frequency
    (2) Fixed dimension
    (3) Change in frequency and dimension
    (4) Change in dimension only
    Answer:
    5. (1) Frequency modulation (FM) conveys information over a carrier wave by varying its instantaneous
    frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant. Frequency modulation is also used in telemetry, radar, seismic prospecting and newborn EEG seizure monitoring. Frequency modulation is known as phase modulation when the carrier phase modulation is the time integral of the FM signal. FM is widely used for broadcasting music and speech, two-way radio systems, magnetic taperecording systems and some video-transmission systems.

    6. When the speed of car is doubled, then what will be the braking force of the car to stop it in the same distance ?

    (1) four times 
    (2) two times
    (3) half 
    (4) one-fourth
    Answer:
    6. (1) Brake force, also known as Brake Power, is a measure of braking power of a vehicle. Suppose a
    car whose mass is ‘x’ and is braked from a speed of y km/hr to come to halt at a uniform retardation in z min. If the speed of the car is doubled in the same distance, then the braking force required to stop the
    car is four times the original speed i.e. ‘4v’. Note that all the parameters remain to be same.

    7. The dimension of which of the following is the same as that of impulse ?

    (1) Volume
    (2) Momentum
    (3) Torque
    (4) Change in the rate of momentum
    Answer:
    7. (2) The quantity of impulse is force × time interval. In classical mechanics, linear momentum or translational momentum is the product of the mass and velocity of an object. For example, a heavy truck moving fast has a large momentum—it takes a large and prolonged force to get the truck up to this speed, and it takes a large and prolonged force to bring it to a stop afterwards. If the truck were lighter or moving slower, then it would have less momentum.

    8. Which among the following is the fundamental quantity ?

    (1) Volume 
    (2) Time
    (3) Velocity 
    (4) Force
    Answer:
    8. (2).The fundamental qualities of Physics are the seven basic quantities that can be used to express all other physical quantities. These are as follows: Length: Metre, Heat: Kelvin, Time: second, Luminous
    Intensity: Candela, Mass: Kilogram, Electric Current: Ampere, and Amount of substance: Moles.

    9. When a ring of metal is heated what happens to its hole ?

    (1) expands
    (2) contracts
    (3) it expands or contracts according to its diameter
    (4) it expands or contracts according to its coefficient of expansion
    Answer:
    9. (1) The hole size will increase because in expansion the size between two molecules do not increase so when the molecules on the outer edge move outward. Due to expansion, the size of the hole will also increase so as to compensate the distance change between the molecules. Thermal expansion is the tendency of matter to change in volume in response to a change in temperature. When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation.

    10. If the diameter of a capillary is doubled, then the rise of water in it will be

    (1) two times 
    (2) half
    (3) four times 
    (4) no change
    Answer:
    10. (2) Radius of a capillary tube is inversely proportional to the height of the liquid column. So, if radius of the tube is doubled, rise of level of water will becomes half of the previous rise in capillary tube. Capillary action, or capillarity, is the ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to external forces like gravity. The effect can be seen in the drawing up of liquids between the hairs of a paint-brush, in a thin tube, in porous materials such as paper, in some non-porous materials such as liquefied carbon fiber, or in a cell. It occurs because of inter-molecular attractive forces between the liquid and solid surrounding surfaces.

    11. Why the needle of iron swims on water surface when it is kept gently ?

    (1) It will remain under the water, when it will displace more water than its weight
    (2) the density of needle is less than that of water
    (3) due to surface tension
    (4) due to its shape
    Answer:
    11. (3) According to Archimedes principle and we can note that the amount of water displaced by a needle is lesser than the amount of water moved out by the needle (that is displacement of the needle). So the needle initially stays on the surface of the water and then sinks into the water. Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in the floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects (e.g. water striders) to run on the water surface. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids.

    12. The mass of a star is two times the mass of the Sun. How it will come to an end ?

    (1) Neutron Star
    (2) Black hole
    (3) White Dwarf
    (4) Red Giant
    Answer:
    12. (1) The mass of a star which is two times the mass of the sun turns into a neutron star. A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with slightly larger mass than protons. Neutron stars are very hot and are supported against further collapse by quantum degeneracy pressure due to the Pauli’s exclusion principle. This principle states that no two neutrons (or any other fermionic particles) can occupy the same place and quantum state simultaneously. A typical neutron star has a mass between about 1.4 and 3.2 solar masses ( Chandrasekhar Limit), with a corresponding radius of about 12 km if the Akmal– Pandharipande–Ravenhall equation of state (APR EOS) is used.

    13. Rain drops fall from great height. Which among the following statements is true regarding it?

    (1) they fall with that ultimate velocity, which are different for different droplets
    (2) they fall with same ultimate velocity
    (3) their velocity increases and they fall with different velocity on the earth
    (4) their velocity increases and they fall with same velocity on the earth
    Answer:
    13. (1) Any mass is attracted to the Earth by the pull of gravity. Gravity accelerates all objects towards the ground at a specific rate. Without any other forces present, the speed of an object in free fall will increase the farther or longer it falls. In general the air resistance on an object depends upon several
    variables. First, it depends upon the shape of the object. Its shape determines the object’s drag coefficient: the more aerodynamic the shape, the less drag. Second, it depends upon the size of the object; specifically the cross-sectional area presented to the airflow (perpendicular to the direction of travel). And lastly, it depends upon the speed of the object. At low speeds the object’s resistance is directly proportional to speed, and at higher speeds the object’s resistance is proportional to its speed
    squared. Most objects falling through the air would be considered to be moving at a higher speed, even
    though that speed might not be great compared to some velocities.

    14. On which of the following techniques photostate machine works ?

    (1) Magnetic Image—Making
    (2) Thermal Image—Making
    (3) Electrostatic Image—Making
    (4) Electromagnetic Image—Making
    Answer:
    14. (3) All Electrostatic Copiers work under the premise that a charge of electricity is placed on an Image Drum which has the ability to retain the electric charge much like a capacitor holds its charge but with the ability to hold or release the charge depending on how much light and darkness is applied to the Image Drum. A photocopier (also known as a copier or copy machine) is a machine that makes paper copies of documents and other visual images quickly and cheaply. Most current photocopiers use a technology called xerography, a dry process using heat. Copiers can also use other technologies such as ink jet, but xerography is standard for office copying.

    15. One Kilowatt hour is equal to—

    (1) 3.6 Mega Joule
    (2) 3.8 Mega Joule
    (3) 3.2 Mega Joule
    (4) 4.0 Mega Joule
    Answer:
    15. (1) The energy 1 kilowatt-hour (kWh) is 3600000 joules or 3.6 mega joule. In physics, energy is an
    indirectly observed quantity that is often understood as the ability of a physical system to do work on
    other physical systems. However, this must be understood as an overly simplified definition, as the
    laws of thermodynamics demonstrate that not all energy can perform work.

    16. What is the minimum escape velocity of rocket to be launched into space ?

    (1) 5 Km/Sec. 
    (2) 6 Km/Sec.
    (3) 11 Km/Sec.
    (4) 15 Km/Sec.
    Answer:
    16. (3) On the surface of the Earth, the escape velocity is about 11.2 kilometers per second (~6.96 mi/s),
    which is approximately 34 times the speed of sound (Mach 34) and several times the muzzle velocity of a rifle bullet (up to 1.7 km/s). However, at 9,000 km altitude in “space”, it is slightly less than 7.1 km/s.
    In physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero. It is the speed needed to “break free” from a gravitational field without further propulsion. A rocket moving out of gravity well does not actually need to attain escape velocity to do so, but could achieve the same result at any speed with a suitable mode of propulsion and sufficient fuel. Escape velocity only applies to ballistic trajectories.

    17. Which of the following statements is true when we see ‘rainbow’ ?

    (1) We face sun and raindrops
    (2) The Sun remains behind us and we face raindrops
    (3) In light rainfall, we face Sun
    (4) The sky remains clear and the sun is at lower position in the sky
    Answer:
    17. (2) We see rainbows because of the geometry of raindrops. When the sun shines from behind us into
    the rain, incident rays of light enter the drop and are refracted inwards. They are reflected from the back
    surface of the raindrop, and refracted again as they exit the raindrop and return to our eyes. A rainbow
    is an optical and meteorological phenomenon that is caused by reflection of light in water droplets in the Earth’s atmosphere, resulting in a spectrum of light appearing in the sky.

    18. How much calorie of energy is released by a boiled egg ?

    (1) 40 
    (2) 50
    (3) 60 
    (4) 77
    Answer:
    18. (4) 77-78 calories are released in a large size boiled egg. Boiled eggs are eggs (typically chicken eggs) cooked by immersion in boiling water with their shells unbroken.

    19. The splitting of different colours of light in a prism is :

    (1) Reflection of light
    (2) Disperson of light
    (3) Diffraction of light
    (4) Refraction of light
    Answer:
    19. (2) The refractive index of many materials (such as glass) varies with the wavelength or colour of the light used, a phenomenon known as dispersion. This causes light of different colours to be refracted
    differently and to leave the prism at different angles, creating an effect similar to a rainbow. In optics,
    dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency, or
    alternatively when the group velocity depends on the frequency. Media having such a property are termed dispersive media. Dispersion is sometimes called chromatic dispersion to emphasize its wavelengthdependent nature, or group-velocity dispersion (GVD) to emphasize the role of the group.

    20. A boat will submerge when it displaces water equal to its own:

    (1) volume 
    (2) weight
    (3) surface area 
    (4) density
    Answer:
    20. (2) A boat will float when the weight of the water it displaces equals the weight of the boat and anything will float if it is shaped to displace its own weight of water before it reaches the point where it will submerge. Floating of the boat works on the principle of buoyancy force which is an upward force exerted by a liquid, gas or other fluid, that opposes the weight of an immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the column than at the top. This difference in pressure results in a net force that tends to accelerate an object upwards.

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