Physics GK Quiz-11

Physics GK Quiz-11

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

    201. Pipelines in cold countries often burst in winter, because

    (1) water freezes and expands in its volume
    (2) temperature of ice is less than that of water
    (3) pipelines contract in their volume
    (4) pipelines expand due to freezing
    Answer:
    201. (1) Water expands on freezing. When liquid water is cooled, it contracts like one would expect until a temperature of approximately 4 degrees Celsius is reached. After that, it expands slightly until it reaches the freezing point, and then when it freezes it expands by approximately 9%. The fact that water expands upon freezing causes icebergs to float.

    202. When a body is taken from earth to moon

    (1) mass changes but weight remains same
    (2) weight changes but mass remains same
    (3) both weight and mass change
    (4) both weight and mass remain same
    Answer:
    202. (2) Mass is how much stuff we are made of, and it is the same whether we are on Earth, on the moon, on Mercury, or anywhere else one can think of. We are held on Earth by gravity. Gravity pulling on mass is our weight .The amount gravity pulls on us anywhere depends on our mass and the mass of the other object (and how far apart the objects are). The moon is smaller than Earth and has a smaller mass, so the moon won’t pull on us as much if we are standing on it. The moon’s gravity is about 1/6 that of Earth’s gravity. Weight is what we get when we stand on a scale. If we were to weigh ourselves on a scale on earth and then could take that same scale to the moon and weigh ourselves there, the weight read on the moon would be 1/6 your earth weight.

    203. A mirage occurs because of

    (1) reflection by hot ground
    (2) total internal reflection by layers of air
    (3) interference of light
    (4) diffraction of light
    Answer:
    203. (2) A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce
    a displaced image of distant objects or the sky. Mirages can be categorized as “inferior” (meaning
    lower), “superior” (meaning higher) and “Fata Morgana”, one kind of superior mirage consisting of
    a series of unusually elaborate, vertically-stacked images, which form one rapidly-changing mirage. Cold air is denser than warm air and has therefore a greater refractive index. As light passes from colder air across a sharp boundary to significantly warmer air, the light rays bend away from the direction of the temperature gradient. When light rays pass from hotter to cooler, they bend toward the direction of the gradient. If the air near the ground is warmer than that higher up, the light ray bends in a concave, upward trajectory. Once the rays reach the viewer’s eye, the visual cortex interprets it as if it traces back along a perfectly straight “line of sight”.

    204. Atomic power plant works on the principle of

    (1) fission
    (2) fusion
    (3) thermal combustion
    (4) combined effect of all the above three
    Answer:
    204. (1) A nuclear power plant is a facility at which energy released by the fissioning of atoms is converted to electrical energy under strictly regulated operating conditions. The major processes are the same as those in nonnuclear (conventional) power plants except that the coal or oil fired boiler is replaced by a nuclear reactor.

    205. Bolometer is used to measure

    (1) Frequency
    2) Temperature
    (3) Velocity 
    (4) Wavelength
    Answer:
    205. (2) A bolometer is a device for measuring the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. A bolometer consists of an absorptive element, such as a thin layer of metal, connected to a thermal reservoir (a body of constant temperature) through a thermal link. The result is that any radiation impinging on the absorptive element raises its temperature above that of the reservoir — the greater the absorbed power, the higher the temperature.

    206. ATM stands for

    (1) Automatic Teller Machine
    (2) Automated Teller Machine
    (3) Automatic Tally Machine
    (4) Automated Tally Mechanism
    Answer:
    206. (1) An automated teller machine or automatic teller machine (ATM) is a computerized telecommunications device that provides the clients of a financial institution with access to financial transactions in a public space without the need for a cashier, human clerk or bank teller. ATMs are known by various other names including ATM machine, automated banking machine, “cash dispenser” (Germany) and various regional variants derived from trademarks on ATM systems held by particular banks.

    207. A person is hurt on kicking a stone due to

    (1) Inertia 
    (2) Velocity
    (3) Reaction 
    (4) Momentum
    Answer:
    207. (3) Newton’s third law states that “For every action, there is an equal and opposite reaction.” The
    statement means that in every interaction, there is a pair of forces acting on the two interacting objects.
    The size of the forces on the first object equals the size of the force on the second object. The direction
    of the force on the first object is opposite to the direction of the force on the second object. So harder
    the stone is kicked, the harder will be its effect on the hitter.

    208. The fuse in our domestic electric circuit melts when there is a high rise in

    (1) Inductance
    (2) Current
    (3) Resistance
    (4) Capacitance
    Answer:
    208. (2) In electronics and electrical engineering, a fuse is a type of low resistance resistor that acts as a
    sacrificial device to provide over-current protection, of either the load or source circuit. It’s essential
    component is a metal wire or strip that melts when too much current flows, which interrupts the circuit
    in which it is connected. Short circuit, overloading, mismatched loads or device failure are the prime
    reasons for excessive current. A fuse interrupts excessive current (blows) so that further damage by
    overheating or fire is prevented.

    209. Which of the following is an example for cantilever beam?

    (1) Diving board
    (2) Bridge
    (3) See-saw
    (4) Common balance
    Answer:
    209. (2) A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs. This is in contrast to a simply supported beam such as those found in a post and lintel system. A simply supported beam is supported at both ends with loads applied between the supports. Cantilevers are widely found in construction, notably in cantilever bridges.

    210. It is difficult to cook rice

    (1) at the top of a mountain
    (2) at the sea level
    (3) under a mine
    (4) same anywhere
    Answer:
    210. (1) On a mountain top the air pressure is a little lower. At higher elevations, water boils at a little lower temp than 100 degrees C. On a mountain top cooking takes longer, because it is like cooking on medium heat, instead of leaving the burner on high. Either way it will cook, one will take longer than the other. The boiling point of water in mountainous areas is lower because of a decreased air pressure (compared to sea level) at higher altitudes.

    211. A dynamo is a device which

    (1) creates mechanical energy
    (2) creates electrical energy
    (3) converts mechanical energy into electrical energy
    (4) converts electrical energy into mechanical energy
    Answer:
    211. (3) A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter. Today, the simpler alternator dominates large scale power generation, for efficiency, reliability and cost reasons. A dynamo has the disadvantages of a mechanical commutator. Also, converting alternating to direct current using power rectification devices (vacuum tube or more recently solid state) is effective and usually economic.

    212. A soap bubble shows colours when illuminated with white light. This is due to

    (1) Diffraction
    (2) Polarisation
    (3) Interference
    (4) Reflection
    Answer:
    212. (3) The iridescent colours of soap bubbles are caused by interfering of (internally and externally) reflected light waves and are determined by the thickness of the film. This phenomenon is not the same as the origin of rainbow colours (caused by the refraction of internally reflected light), but rather are the same as the phenomenon causing the colours in an oil slick on a wet road. As light impinges on the film some of it reflects off of the outer surface, some of it enters the film and reemerges after reflecting off the second surface, some of it enters the film and reemerges after bouncing back and forth between the two surfaces from 1 to n times. The total reflection observed is determined by the interference of all these reflections.

    213. The instrument used to see the distant objects on the Earth is

    (1) Terrestrial telescope
    (2) Astronomical telescope
    (3) Compound microscope
    (4) Simple microscope
    Answer:
    213. (1) A telescope assists the eye chiefly in two way by enlarging the visual angle under which a distant object is seen, and thus magnifying that object; and, secondly, by collecting, and conveying to the eye, a larger beam of light than would enter the naked organ, thus rendering objects distinct and visible which would otherwise be indistinct and or invisible. It’s essential parts are the object glass, or concave mirror, which collects the beam of light, and forms an image of the object, and the eyeglass, which is a microscope, by which the image is magnified. Terrestrial telescope is a telescope whose eyepiece has one or two lenses more than the astronomical, for the purpose of inverting the image and exhibiting objects erect. The terrestrial telescope is also known as the spyglass.

    214. Global warming is expected to result in

    (1) increase in level of sea
    (2) change in crop pattern
    (3) change in coast line
    (4) All of the above
    Answer:
    214. (4) Global warming is the rise in the average temperature of Earth’s atmosphere and oceans since
    the late 19th century and its projected continuation. Since the early 20th century, Earth’s mean surface
    temperature has increased by about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980. The effects of an increase in global temperature include a rise in sea levels and a change in the amount and pattern of precipitation, as well a probable expansion of subtropical deserts. Other likely effects of the warming include a more frequent occurrence of extreme-weather events including heat waves, droughts and heavy rainfall, ocean acidification and species extinctions due to shifting temperature regimes. Effects significant to humans include the threat to food security from decreasing crop yields and the loss of habitat from inundation.

    215. Which of the following liquids has the least density ?

    (1) Fresh water
    (2) Salt water
    (3) Petrol
    (4) Mercury
    Answer:
    215. (3) Gasoline or petrol is a transparent, petroleumderived liquid that is used primarily as a fuel in
    internal combustion engines. It consists mostly of organic compounds obtained by the fractional
    distillation of petroleum, enhanced with a variety of additives. The specific gravity (or relative density) of gasoline ranges from 0.71–0.77 kg/l (719.7 kg/m3 ; 0.026 lb/in3; 6.073 lb/US gal; 7.29 lb/imp gal),
    higher densities having a greater volume of aromatics. Gasoline floats on water; water cannot generally be used to extinguish a gasoline fire, unless used in a fine mist.

    216. Which of the following principle is used to produce ‘low-temperatures’ ?

    (1) Super conductivity
    (2) Joule-Kelvin effect
    (3) Thermo-electric effect
    (4) Adiabatic demagneti-sation
    Answer:
    216. (4) Magnetic refrigeration is a cooling technology based on the magneto-caloric effect. This technique can be used to attain extremely low temperatures, as well as the ranges used in common refrigerators, depending on the design of the system. The magnetocaloric effect (MCE, from magnet and calorie) is a magneto-thermodynamic phenomenon in which a change in temperature of a suitable material is caused by exposing the material to a changing magnetic field. This is also known by low temperature physicists as adiabatic demagnetization, due to the application of the process specifically to create a temperature drop.

    217. A photo-electric cell converts

    (1) mechanical energy to electric energy
    (2) heat energy to mechanical energy
    (3) light energy to chemical energy
    (4) light energy to electrical energy
    Answer:
    217. (4) Photoelectric cell or photocell, device whose electrical characteristics (e.g., current, voltage, or
    resistance) vary when light is incident upon it. The most common type consists of two electrodes
    separated by a light-sensitive semiconductor material. A battery or other voltage source connected to the electrodes sets up a current even in the absence of light; when light strikes the semiconductor section of the photocell, the current in the circuit increases by an amount proportional to the intensity of the light.

    218. Two stones of different masses are dropped simultaneously from the top of a building

    (1) Smaller stone reaches the ground earlier
    (2) Larger stone reaches the ground earlier
    (3) Both the stones reach the ground at the same time
    (4) Depends on the composition of the stone
    Answer:
    218. (3) Both stones at the same time. The initial speed is 0 for both stones, and the only acceleration working in that system would be g (Gravity acceleration). So, as the distance is the same, the final speed will be the same time. The only reason which could change this result is a difference in the shape of the stones. While they fall to the ground, they must “open” a way across the air. The shape of the falling object will decide the force needed to open that way. This is called the “Air resistance”. Depending on the shape of the object, the resistance force will be bigger or smaller. As this force works counter to g, the falling time will decrease. Between a feather and a plumb ball, the falling time will be the same in vacuum, but inside air, the resistance force for the feather has almost the same value than gravity, while for the ball, the resistance is very much weaker than gravity.

    219. The ozone hole that has been detected lies in the atmosphere above

    (1) Arctic Ocean
    (2) Antarctica
    (3) India
    (4) Alaska
    Answer:
    219. (2) Ozone layer, that is, the layer of life-protecting ozone found at the top of the stratosphere.  Ozone is formed in the earth’s stratosphere and is critical tolife on earth as we know it. There is compelling scientific evidence that ozone is destroyed in the stratosphere and that some human-released
    chemicals are speeding up the breakdown of ozone in the atmosphere. The appearance of a hole in the
    earth’s ozone layer over Antarctica, first detected in 1976, was so unexpected that scientists didn’t pay
    attention to what their instruments were telling them; they thought their instruments were malfunctioning.

    220. The device used to change the speed of an electric fan is

    (1) Amplifier 
    (2) Regulator
    (3) Switch 
    (4) Rectifier
    Answer:
    220. (2) A voltage regulator is designed to automatically maintain a constant voltage level. A voltage regulator may be a simple “feed-forward” design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages. Electronic voltage regulators are found in devices such as computer power supplies where they stabilize the DC voltages used by the processor and other
    elements.

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