Physics GK Quiz-23

Physics GK Quiz-23

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

    441. As we go from Equator to North pole the value of ‘g’, the acceleration due to gravity

    (1) remains the same
    (2) decreases
    (3) increases
    (4) None of the above
    Answer:
    441. (3) The acceleration due to gravity of earth is the rate of increase of velocity of a body falling freely towards the earth. At a given place, the value of acceleration due to gravity is constant but it varies from one place to another place on the earth surface. It is due to this fact that earth is not a perfect sphere. It is flattened at the poles and bulges out at the equator. The value of ‘g’ is minimum at the equator and maximum at the poles.

    442. Shaving mirror is

    (1) Convex 
    (2) Concave
    (3) Plane 
    (4) Parabolic
    Answer:
    442. (2) Concave mirrors are used in makeup or shaving mirrors. When shaving or applying makeup, a person holds the mirror close to her face. This allows him to see an enlarged image of him face, which is helpful for applying makeup or shaving correctly.

    443. Magnifying Glass is basically a

    (1) Plano-concave lens
    (2) Concave lens
    (3) Convex lens
    (4) Cylindrical lens
    Answer:
    443. (3) A magnifying glass is a convex lens that is used to produce a magnified image of an object. The magnification of a magnifying glass depends upon where it is placed between the user’s eye and the object being viewed, and the total distance between them.

    444. Water will not be vapourised if

    (1) the temperature is 0°C
    (2) the humidity is 0%
    (3) the humidity is 100%
    (4) the temperature is 100°C
    Answer:
    444. (3) If the relative humidity is 100 percent, water will not evaporate as the air is already saturated with moisture. When relative humidity approaches 100 percent, condensation can occur. The lower the relative humidity, the easier it is for moisture to evaporate.

    445. Which of the following is not a part of a CRT ?

    (1) Phosphor screen
    (2) Shadow mask
    (3) Electron gun
    (4) Gas plasma
    Answer:
    445. (4) The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons or electron emitter) and a fluorescent screen used to view images. Colour tubes use three different
    phosphors which emit red, green, and blue light respectively. They are packed together in stripes (as
    in aperture grille designs) or clusters called “triads” (as in shadow mask CRTs).

    446. Railway tracks are banked on curves so that

    (1) Necessary centrifugal force may be obtained from the horizontal component of the weight of the train
    (2) No frictional force may be produced between the tracks and the wheels of the train
    (3) Necessary centripetal force may be obtained from the horizontal component of the weight of the train
    (4) The train may not fall down inwards
    Answer:
    446. (3) Railway tracks are banked on curves so that necessary centripetal force may be obtained from the horizontal component of the weight of the train. It helps the train to stay on the track as it negotiates
    the curve. The raised track provides required centripetal force to enable it to move round the curve.

    447. The pitch of sound depends on its

    (1) Frequency
    (2) Intensity
    (3) Velocity 
    (4) Amplitude
    Answer:
    447. (1) Pitch is a perceptual property that allows the ordering of sounds on a frequency-related scale. Pitch may be quantified as a frequency, but pitch is not a purely objective physical property; it is a subjective psycho-acoustical attribute of sound. When the frequency is high, the wavelength of the sound is shorter.

    448. Which of the following is a conductor of electricity ?

    (1) Rubber 
    (2) Pure water
    (3) Salt water 
    (4) Benzene
    Answer:
    448. (3) Pure water is actually an extremely poor conductor, but saturated salt water is a good conductor. The saltier the water, the better the conductance. The reason it conducts electricity is because the NaCl (sodium chloride) breaks apart into a positively charged Na+ and a negatively charged Chlorine Cl-. When current is applied, it is easily conducted by the highly charged ions.

    449. The working of a rocket is based on the principle of:

    (1) Conservation of momentum
    (2) Conservation of mass
    (3) Conservation of energy
    (4) Conservation of angular momentum
    Answer:
    449. (1) The operation of a rocket illustrates the conservation of momentum. Just before launching, the momentum of the rocket is zero. When the rocket is fired, it forces a jet of hot gases with a high velocity through the nozzle. The jet of gases acquires a momentum downwards. Hence, the rocket acquires a momentum of equal magnitude in opposite direction. Thus the rocket moves upwards.

    450. A fuse wire is made of:

    (1) an alloy of tin and copper
    (2) an alloy of tin and lead
    (3) an alloy of tin and aluminium
    (4) an alloy of nickel and chromium
    Answer:
    450. (2) Electric fuse wire is an alloy made of tin (63 % & lead 37 %. The cross sectional area determines the melting point at a certain current. Alloys (e.g. tin/ lead) are used due to their ‘eutectic’ action -i.e. the resulting combination of good conductivity (due to the tin) with a low melting point due to the lead).

    451. The energy that can harness heat stored below the earth’s surface is known as ;

    (1) thermal energy
    (2) nuclear energy
    (3) tidal energy
    (4) geo-thermal energy
    Answer:
    451. (4) Geothermal energy is thermal energy generated and stored in the Earth. The Geothermal energy of the Earth’s crust originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%).Current worldwide installed capacity is 10,715 megawatts (MW), with the largest capacity in the United States (3,086 MW), Philippines, and Indonesia.

    452. The temperature of boiling water in a steam engine may be high because :

    (1) there are dissolved substances in water
    (2) there is low pressure inside the boiler
    (3) there is high pressure inside the boiler
    (4) the fire is at very high temperature
    Answer:
    452. (3) In the boiler of a steam engine, there is a firebox where coal is shoveled into. The coal is kept burning at a very high temperature, and is used to heat the boiler to boil water producing a high pressure steam. The high-pressure steam expands and exits the boiler via steam pipes into the steam reservoir, the steam is then controlled by a slide valve to move into a cylinder to push the piston. The pressure of the steam energy pushing the piston turns the drive wheel in a circle, creating motion for the locomotive.

    453. An instrument used to measure humidity is:

    (1) Anemometer
    (2) Hygrometer
    (3) Thermometer
    (4) Pyrheliometer
    Answer:
    453. (2) A hygrometer is an instrument used for measuring the moisture content in the environment. Humidity measurement instruments usually rely on measurements of some other quantity such as
    temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed.

    454. Fat can be separated from milk in a cream separator because of:

    (1) Cohesive force
    (2) Gravitational force
    (3) Centripetal force
    (4) Centrifugal force
    Answer:
    454. (4) The separation of fat from milk is based on the fact that when liquids of different specific gravities revolve around the same centre at the same distance with the same angular velocity, a greater centrifugal force is exerted on the heavier liquid than on the lighter one.

    455. A transformer works with

    (1) alternating current only
    (2) direct current only
    (3) both AC and DC
    (4) any signal
    Answer:
    455. (1) Transformer, a device that transfers electric energy from one circuit to another, usually with a change in voltage. Transformers work only with a varying electric current, such as alternating current (AC). Transformers are important in the distribution of electric power.

    456. In the Earth, the weight of a body is maximum at the

    (1) North Pole
    (2) South Pole
    (3) Equator 
    (4) Surface
    Answer:
    456. (4) If the mass of the body is m, the force of attraction of the earth, or the weight w of the body, is given by the Newton’s law of gravitation as w = mg, with acceleration due to gravity g = GM R2 where M and R are the mass and radius of the Earth respectively. Since weight of the body is directly proportional to g, the weight of the body is maximum at the centre of the earth and zero at the centre of the earth.

    457. The technique of collecting information about an object from a distance without making physical contact with it is

    (1) Remote sensing
    (2) Remote control
    (3) Remote accessing
    (4) Space shuttle
    Answer:
    457. (1) Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth by means of propagated signals (e.g. electromagnetic radiation emitted from aircraft or satellites).

    458. The head mirror used by ENT doctors is

    (1) Concave 
    (2) Convex
    (3) Plane 
    (4) Plano-convex
    Answer:
    458. (1) A head mirror is mostly used for examination of the ear, nose & throat. It comprises a circular concave mirror, with a small hole in the middle, and is attached to a head band. The mirror is worn over the physician’s eye of choice, with the concave mirror surface facing outwards and the hole directly over the physician’s eye, providing illumination like a ring light.

    459. Direct conversion of solar energy with the use of a photo voltaic cell results in the production of

    (1) Optical energy
    (2) Electrical energy
    (3) Thermal energy
    (4) Mechanial energy
    Answer:
    459. (2) A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect. It is a form of photoelectric cell (in that its electrical characteristics—e.g. current, voltage, or resistance— vary when light is incident upon it) which, when exposed to light, can generate and support an electric current without being attached to any external voltage source.

    460. A man inside an artificial satellite feels weightlessness because the force of attraction due to earth is

    (1) zero at that place
    (2) is balanced by the force of attraction due to moon
    (3) equal to the centripetal force
    (4) non-effective due to particular design of the satellite
    Answer:
    460. (1) Earth attracts all bodies towards its centre. The acceleration produced in the body due to attraction force of earth on it is called the acceleration due to gravity. A astronaut in a satellite experiences weightlessness because two forces act on him: gravitational pull and centrifugal force which cancel out each other with the resultant force acting on him being zero.

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