# Physics Solved MCQs

1.

## A light year is a measure of :

A. Speed
B. Velocity
C. Distance
D. Time
Explanation: A light-year is a unit of length equal to just under 10 trillion kilometres (or about 6 trillion miles). As defined by the International Astronomical Union (TAU), a light-year is the distance that light travels in a vacuum in one Julian year. Note that the lightyear is a measure of distance (rather than, as is sometimes misunderstood, a measure of time).
2.

## A device which is used to limit the current in an electrical circuit is called a -

A. Grid
B. Fuse
C. Hub
D. Conductor
Explanation: A fuse places a limit on the amount of current that can be drawn by an electric circuit by opening (blowing or melting) when the current exceeds a preset limit. This protects the circuit and the surroundings from fire or damage in the case of an overload or short circuit.
3.

## Two rods, one of copper and other of steel, experience the same up thrust when placed in water. Thus, both have –

A. equal volume
B. equal weight
C. equal density
D. equal mass
Explanation: When a body is placed in water, the upthrust or buoyant force acting on it depends upon the following factors: (1) Volume of the body submerged in the liquid - (V), or volume of the liquid displaced - (V); (ft) Density of the liquid - (d); and (Hi) Acceleration due to gravity In-line.
4.

## Minimum numbers of unequal vectors which can give zero resultant are -

A. Two
B. Three
C. Four
D. More than four
Explanation: Minimum number of unequal vectors which can give three zero resultants.
5.

## Water is not suitable as a calorimetric substance because it –

A. has high specific heat
B. is a good conductor
C. has high boiling point
D. low latent heat of vaporization
Answer» A. has high specific heat
Explanation: The specific heat of water is higher than all other common substances. Hence, water is used for heating purposes (as in hot water bottles) and for cooling purposes (as in radiators of cars). Off all the liquids, mercury has the lowest specific heat due to which it is used as a thermometric liquid.
6.

## When a body falls from an aeroplane, there is increase in its –

A. Kinetic energy
B. Mass
C. Acceleration
D. Potential energy
Explanation: The energy possessed by a body by virtue of its motion is called kinetic energy. Potential Energy is the energy possessed by virtue of its position or configuration. When a body falls from an aeroplane, there is increase in its acceleration.
7.

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

A. Coal
B. Lignite
C. Anthracite
D. Pit
Explanation: 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 ("coal-like") 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.
8.

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

A. Micro waves
C. A. M.
D. Frequency of 1016 series
Explanation: 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 hand-held terminals, and for TV and radio broadcasting. Microwave technology is extensively used for point-to-point telecommunications (i.e., non broadcast uses).
9.

## Energy is continuously created in the sun due to –

A. Nuclear fusion
B. Nuclear fission
Explanation: The central mass of the sun becomes increasingly hot and dense. eventually initiating thermonuclear fusion in its core. It is thought that almost all other stars form by this process. nuclear fusion is a nuclear reaction in which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy which is released.
10.

## When the barometer reading dips suddenly, it is an indication of –

A. Hot weather
B. Calm weather
C. Storm
D. Dry weather
Explanation: Sudden and great fluctuations of the barometer at any time of the year indicate unsettled weather for several days, perhaps a fortnight. If the barometer falls two or threetenths of an inch in four hours, one can expect a gale of wind. If the surface of the mercury in the cistern of the barometer vibrates upon the approach of a storm, the gale can be expected to be severe.
11.

## Good conductor of electricity is –

A. dry air
B. paper
C. kerosene
D. graphite
Explanation: Graphite has a tendency to behave very much like a metal because the carbon molecules arrange themselves into a lattice structure. The crystal lattice is the same orientation that metal forms, and it allows the free-movement of electrons, making it a good electrical conductor. The characteristics possesses by the graphite for conduction is far better than the dry air paper and kerosene and that's what makes it a good conductor.
12.

## The fourth state of matter is known as

A. Gas
B. Vapour
C. Plasma
D. Electrons
Explanation: The characteristics of plasmas are significantly different from those of ordinary neutral gases so that plasmas are considered a distinct "fourth state of matter, plasma is a state of matter similar to gas in which a certain portion of the particles is ionized. Heating a gas may ionize its molecules or atoms (reduce or increase the number of electrons in them), thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions.
13.

## Radio waves, microwaves, infra-red spectrum, ultraviolet rays, X-rays and gamma rays are classified as ______.

A. light waves
B. electromagnetic waves
C. electric waves
D. magnetic waves
Explanation: Electromagnetic radiation is the radiant energy released by certain electromagnetic processes. It consists of electromagnetic waves which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light through a vacuum.
14.

## Which one of the following instruments is used to study dispersion of light?

A. Microscope
B. Telescope
C. Spectrometer
D. Photometer
Explanation: Dispersion occurs when different frequencies of light have different phase velocities, due either to material properties (material dispersion) or to the geometry of an optical waveguide (waveguide dispersion). A spectrometer (spectro-photometer, spectrograph or spectroscope) is an instrument used to measure properties alight over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials.
15.

## A falling drop of rain water ac-quires the spherical shape due to –

A. Viscosity
B. Surface Tension
C. Atmospheric pressure
D. Gravitational force
Explanation: Raindrops start out as round high in the atmosphere as water collects on dust and smoke particles in clouds. But as raindrops fall, they lose their rounded shape. A raindrop falling through the atmosphere forms as a roughly spherical structure due to the surface tension of water. This surface tension is the "skin" of a body of water that makes the molecules stick together. The cause is the weak hydrogen bonds that occur between water molecules.
16.

## This scientist gave the law- ‘Properties of elements are a periodic function of their atomic number.’ This property of the fundamental importance of atomic number was discovered by-

A. Johann Wolfgang Döbereiner
B. John Newlands
C. Dmitri lvanovich Mendeléev
D. Henry Moseley
Explanation: In 1913, Henry Moseley showed that the atomic number of an element is a more fundamental property than its atomic mass as described below.
17.

## The mass and energy equivalent to 1 a.m.u. respectively are -

A. 1.67 x 10−27 g, 9.30 MeV
B. 1.67 x 10−27kg, 930 MeV
C. 1.67 x 10−27kg, 1 MeV
D. 1.67 x 10−34 kg, 1 MeV
Answer» B. 1.67 x 10−27kg, 930 MeV
Explanation: The mass and energy equivalent to 1 a.m.u. respectively are 1.67 x 10−27kg, 930 MeV.
18.

## A spherical ball made of steel when dropped in mercury container will –

A. sink in mercury
B. will be on the surface of mercury
C. will be partly immersed mercury
D. will dissolve in mercury
Answer» B. will be on the surface of mercury
Explanation: The density of steel usually ranges between 7.75 and 8.05 g/cm3 and the density of mercury is 13.534 g/cm3. Mercury is denser than steel this will mean that the buoyant force is large enough to float the steel ball. Different materials usually have different densities, so density is an important concept regarding buoyancy, purity and packaging.
19.

## The sounds having a frequency of 20 Hertz to 20,000 Hertz are known as –

A. Audible sounds
B. Ultrasonics
C. Infrasonics
D. Megasonics
Explanation: An audio frequency is characterized as a periodic vibration whose frequency is audible to the average human. It is the property of sound that most determines pitch and is measured in hertz (Hz).The generally accepted standard range of audible frequencies is 20 to 20,000 Hz, although the range of frequencies individuals hear is greatly influenced by environmental factors.
20.

## Gamma rays have greatest similarity with –

A. α-rays
B. β-rays
C. X-rays
D. U.V.-rays
Explanation: Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as y, is electromagnetic radiation of high frequency and therefore high energy. Gamma rays are ionizing radiation and are thus biologically hazardous. They are classically produced by the decay from high energy states of atomic nuclei (gamma decay), but are also created by other processes.
21.

## In the absence of ozone layer, Which rays will enter into atmosphere?

A. Infrared
B. Visible
C. Ultraviolet
D. X-rays
Explanation: The ozone layer is a layer in Earth's atmosphere containing relatively high concentrations of ozone (O3). The ozone layer absorbs 97-99% of the Sun's medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which potentially damages exposed life forms on Earth.
22.

## Light year is the unit of -

A. Frequency
B. Distance
C. Energy
D. Power
Explanation: A light-year is a unit of distance. It is the distance that light can travel in one year. Light moves at a velocity of about 300,000 kilometers (km) each second. So in one year, it can travel about 10 trillion km.
23.

## An object at rest will remain at rest and an object in motion will remain in motion until and unless it is acted upon by an external force. This is Newton's –

A. First law
B. Second law
C. Third law
D. Fourth law
Explanation: Newton's first law of motion -sometimes referred to as the law of inertia-states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This is normally taken as the definition of inertia.
24.

A. γ – ray
B. X – ray
C. α – ray
D. β – ray