Physics GK Quiz-8

Physics GK Quiz-8

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

141. The instrument used to measure the speed of the wind is

(1) Altimeter
(2) Anemometer
(3) Chronometer
(4) Dosimeter
141. (2) An anemometer is a device for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos, meaning wind, and is used to describe any airspeed measurement instrument used in meteorology or aerodynamics. The first known description of an anemometer was given by Leon Battista Alberti around 1450.

142. Who defined the law of gravitation ?

(1) Newton
(2) Archimedes
(3) Galileo
142. (1) Sir Isaac Newton brought out his monograph, titled ‘Philosophiæ Naturalis Principia Mathematica,’ in 1687. In this work, Newton described universal gravitation and the three laws of motion, which dominated the scientific view of the physical universe for the next three centuries. Newton showed that the motions of objects on Earth and of celestial bodies are governed by the same set of natural laws, by demonstrating the consistency between Kepler’s laws of planetary motion and his theory of gravitation, thus removing the last doubts about helio-centrism and advancing the Scientific Revolution. Newton’s law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

143. The metal used to make lightning conductors is

(1) Iron
(2) Aluminium
(3) Copper
(4) Zinc
143. (3) A lightning rod is a metal rod or metallic object mounted on top of a building, electrically bonded using a wire or electrical conductor to interface with ground or “earth” through an electrode, engineered to protect the building in the event of lightning strike. If lightning targets the building it will preferentially strike the rod and be conducted to ground through the wire, instead of passing through the building, where it could start a fire or cause electrocution. Copper and its alloys are the most common materials used in lightning protection. Copper does not attract lightning, but it effectively and rapidly facilitates the transmission of lightning energy to the ground because of its excellent electrical conductivity and corrosion resistance characteristics. Also, it bends easily compared to other conductor materials.

144. A hydrogen balloon floats up because of

(1) air pressure decreases with decrease in height
(2) air pressure decreases with decrease in weight
(3) weight of the balloon is less than the weight of air displaced by it.
(4) the pressure inside the balloon is more than the pressure outside it
144. (3) A hydrogen atom is very light. Most of the air on earth is made up of nitrogen, oxygen, and carbon dioxide. All of these elements are heavier than hydrogen, so the balloon is pushed upwards.
Hydrogen weighs 0.08988 grams per liter. Nitrogen, which makes up 80% of the air we breathe, weighs
1.2506 grams per liter. Hydrogen filled balloons follow the same principle as we do when we float in the water; the law of buoyancy. If the water we displace weighs more than we do, we will float.

145. In a rechargeable cell what kind of energy is stored within the cell?

(1) Electrical energy
(2) Potential energy
(3) Chemical energy
(4) Kinetic energy
145. (3) In electricity, a battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. A battery is a device that converts chemical energy directly to electrical energy. It consists of a number of voltaic cells; each voltaic cell consists of two half-cells connected in series by a conductive electrolyte containing anions and cations. One half-cell includes electrolyte and the electrode to which anions (negatively charged ions) migrate, i.e., the anode or negative electrode; the other half-cell includes electrolyte and the electrode to which cations
(positively charged ions) migrate, i.e., the cathode or positive electrode. In the redox reaction that powers the battery, cations are reduced (electrons are added) at the cathode, while anions are oxidized (electrons are removed) at the anode.

146. Which one of the following lenses should be used to correct the defect of astigmatism ?

(1) Cylindrical lens
(2) Concave lens
(3) Convex lens
(4) Bifocal lens
146. (1) Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. The two types of astigmatism are regular and irregular. Irregular
astigmatism is often caused by a corneal scar or scattering in the crystalline lens, and cannot be
corrected by standard spectacle lenses, but can be corrected by contact lenses. Regular astigmatism
arising from either the cornea or crystalline lens can be corrected by a toric lens. This optical shape gives rise to regular astigmatism in the eye. Toric lens is somewhat similar in significance to cylindrical cells.

147. Superconductors are those elements

(1) Whose conductivity is intermediate between metals and insulators
(2) Whose resistance falls almost to zero at very low temperatures
(3) which turn into insulators at very low temperatures
(4) which conduct electricity only at super-high temperatures
147. (2) Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The electrical resistivity of a
metallic conductor decreases gradually as temperature is lowered. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current flowing in a loop of superconducting wire can persist indefinitely with no power source.

148. In a Laser (say neon laser) all the atoms emit the light waves of

(1) Same frequency
(2) Same amplitude
(3) Same phase
(4) All of the above
148. (4) In a Laser all the atoms emit the light waves of same frequency, amplitude and phase. A laser is a device that emits light (electromagnetic radiation) through a process of optical amplification based on
the stimulated emission of photons. The term “laser” originated as an acronym for Light Amplification by Stimulated Emission of Radiation.

149. Which of the following has got more heat capacity ?

(1) Iron piece
(2) Water
(3) Gold piece
(4) Benzene
149. (2) Heat capacity (usually denoted by a capital C, often with subscripts), or thermal capacity, is the
measurable physical quantity that characterizes the amount of heat required to change a substance’s
temperature by a given amount. In the International System of Units (SI), heat capacity is expressed in
units of joule(s) (J) per Kelvin (K). Among iron piece, water, gold piece and benzene; water has the
maximum heat capacity i.e. 4.1813 j/g.k.

150. If the temperature of a place increases suddenly, the relative humidity

(1) Increases
(2) Decreases
(3) Remains constant
(4) Fluctuates
150. (2) Relative humidity is the ratio of the partial pressure of water vapor in an air-water mixture to the saturated vapor pressure of water at a prescribed temperature. The relative humidity of air depends not only on temperature but also on the pressure of the system of interest. If the system at State A is isobarically heated (heating with no change in system pressure) then the relative humidity of the system decreases because the saturated vapor pressure of water increases with increasing temperature.

151. Fleming’s right hand rule is used to find the direction of the

(1) Alternate current
(2) Direct current
(3) Induced current
(4) Actual current
151. (3) Fleming’s right hand rule shows the direction of induced current when a conductor moves in a magnetic field. The right hand is held with the thumb, first finger and second finger mutually perpendicular to each other. The rule is named after British engineer John Ambrose Fleming.

(1) Amplitude Movement
(2) Anywhere Movement
(3) Amplitude Matching
(4) Amplitude Modulation
the first method of impressing sound on a radio signal and is still widely used today. An AM receiver detects amplitude variations in the radio waves at a particular frequency. It then amplifies changes in the signal voltage to drive a loudspeaker or earphones. The earliest crystal radio receivers used a crystal diode detector with no amplification.

153. Which colour is the complementary colour of yellow ?

(1) Blue
(2) Green
(3) Orange
(4) Red
153. (1) Complementary colours are pairs of colours that are of “opposite” hue in some colour model. In colour theory, two colours are called complementary if, when mixed in the proper proportion, they produce a neutral colour (grey, white, or black). In roughly-perceptual colour models, the neutral colours (white, grey, and black) lie along a central axis. In the RGB colour model (and derived models such as HSV), primary colours and secondary colours are paired in this way: red and cyan; green and magenta; blue and yellow.

154. During washing of clothes, we use indigo due to its

(1) better cleaning action
(2) proper pigmental composition
(3) high glorious nature
(4) very low cost
154. (2) Indigo is a dye different than any other. It does not require any mordant. Rather it is dyed through a living fermentation process. The process “reduces” the Indigo, changing it from blue to yellow. In this state, it dissolves in an alkaline solution. The fibre is worked in the solution, or “vat”. When brought out to the air, it is a bright green. Slowly the air changes it to the beautiful deep and rich blue of Indigo.

155. The energy stored in a watch spring is

(1) kinetic energy
(2) potential energy
(3) heat energy
(4) chemical energy
155. (2) The energy stored in a spring of a watch is potential energy which is as a result of winding of the string. This energy is used to run the watch as it converts this potential energy to rotational kinetic energy. Windup watches function due to the winding of a small dial on the outside of the watch. This dial transfers the energy produced by your hand to the internal components of the watch.

156. The sensation of weightlessness in a spacecraft in an orbit is due to the

(1) absence of gravity outside
(2) acceleration in the orbit which is equal to the acceleration due to gravity outside
(3) presence of gravity outside but not inside the spacecraft
(4) fact that spacecraft in the orbit has no energy
156. (2) Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person’s body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space. However, a spacecraft needs gravity in order to orbit around the Earth. Gravity supplies a centripetal force which is responsible for the orbital motion. This means that the spacecraft is falling towards the Earth without colliding with it due to tangential velocity. Despite this fact, spacecraft in orbit around Earth still experience a certain amount of weighted force.

157. ‘Therm’ is the unit of

(1) power
(2) heat
(3) light
(4) distance
157. (2) Therm is a non-SI unit of heat energy equal to 100,000 British thermal units (BTU). It is
approximately the energy equivalent of burning 100 cubic feet (often referred to as 1 CCF) of natural gas. Since (Natural Gas) meters measure volume and not energy content, a therm factor is used by (Natural) gas companies to convert the volume of gas used to its heat equivalent, and thus calculate the actual energy use.

158. Newton’s first law of motion gives the concept of

(1) energy
(2) work
(3) momentum
(4) inertia
158. (4) Newton’s laws of motion are three physical laws that form the basis for classical mechanics. They describe the relationship between the forces acting on a body and its motion due to those forces. The first law states that if the net force (the vector sum of all forces acting on an object) is zero, then the
velocity of the object is constant. Newton’s first law is often referred to as the law of inertia. Thus, a
condition necessary for the uniform motion of a particle relative to an inertial reference frame is that
the total net force acting on it is zero.

159. A pond of water appears less deep due to

(1) reflection
(2) diffraction
(3) refraction
(4) polarisation
159. (3) The apparent depth will look less that its real depth due to the refraction of light. First of all, imagine an object at the bottom of the pond, emitting three beams of light: one straight to the centre of your eye, one above your eye, and one below. Now, as light travels faster in air than it does in water, it will accelerate as it breaks the surface, at which point it bends away from the ‘normal’ - the imaginary line perpendicular to the surface. So back to those three beams, the one coming straight at your eye, and as such perfectly vertical, will not bend one way or another as it leaves the water. The other two beams,
however, will bend further away from that middle beam, creating a ‘triangle’ with a larger base, if you
were to draw a diagram. These new trajectories, if traced backwards, and ignoring a reverse bending
in water, will all meet at a new point, higher than the actual point of origin.

160. The oldest type of energy known to man is

(1) wind power
(2) solar power
(3) tidal energy
(4) geothermal energy