Q280. Assertion (A): The temperature of a metal wire rises when an electric current is passed through it. Reason (R): Collision of metal atoms with each other releases heat energy.

Assertion (A): In our houses, the current in the A.C. electricity line changes direction 60 times per second. Reason (R): The frequency of alternating voltage s

Assertion (A): Sodium metal is stored under kerosene. Reason (R): Metallic sodium melts when exposed to air. (a) Both A and R are true and R is the correct expl

Assertion (A): With the increase of temperature, the viscosity of glycerine increases. Reason (R): Rise of temperature increases kinetic energy of molecules. Co

Assertion (A): A piece of copper and a piece of glass are heated to the same temperature. When touched, thereafter, the copper piece appears hotter than the gla

Assertion (A): Unsaturated fats are more reactive compared with the saturated fats. Reason (R): Unsaturated fats have only single bonds in their structure.

Assertion (A): To dilute sulphuric acid, acid is added to water and not water to acid. Reason (R): Specific heat of water is quite large.

Assertion (A): Radio waves bend in a magnetic field. Reason (R): Radio waves are electromagnetic in nature.

Assertion (A): Radio waves bend in a magnetic field. Reason (R): Radio waves are electromagnetic in nature.

Assertion (A): Transformer is useful for stepping up or stepping down voltages. Reason (R): Transformer is a device used in D.C. circuits. In the context of the

Assertion (A): A stick is dipped in water in a slanting position. If observed sideways, the stick appears short and bent at the surface of water. Reason (R): A

Assertion (A): In a motion picture, usually 24 frames are projected every second over the whole length of the film. Reason (R): An image formed on the retina of

Assertion (A): The main constituent of the liquefied petroleum gas is methane. Reason (R): Methane can be used directly for burning in homes and factories where

Given below: Assertion (A): In the periodic table of chemical elements, electron affinity is always found to increase from top to bottom in a group Reason (R):

Assertion (A): Formic acid is a stronger acid than acetic acid. Reason (R): Formic acid is an organic acid. (a) Both A and R are true and R is the correct expla

Assertion (A): Coal-based thermal power stations contribute to acid-rain. Reason (R): Oxides of carbon are emitted when coal burns.

Assertion (A): Amoeba reproduces by fission. Reason (R): All unicellular organisms reproduce by asexual methods.

Assertion (A): Large cold storage plants use ammonia as refrigerant while domestic refrigerators use chlorofluoro- carbons. Reason (R): Ammonia can be liquefied

Assertion (A): Small glass beads fixed on traffic signals glow brightly when light falls upon them. Reason (R): Light is totally reflected when the angle of inc

Assertion (A): A jet aircraft moving at Mach Number equal to 1 travels faster at an altitude of 15 km than while moving at Mach Number equal to 1 near the sea l

Assertion (A): A jet aircraft moving at Mach Number equal to 1 travels faster at an altitude of 15 km than while moving at Mach Number equal to 1 near the sea l

Assertion (A): The boiling point of water decreases as the altitude increases. Reason (R): The atmospheric pressure increases with altitude. Codes: (a) Both A a

Assertion (A): To orbit around the Sun the planet Mars takes lesser time than the time taken by the earth. Reason (R): The diameter of the planet Mars is less t

Which one of the following is printed on a commonly used fluorescent tube light?

What is the order of magnitude of electric resistance of the human body (dry)?

Two wires have their lengths, diameters and resistivities all in the ratio of 1: 2 If the resistance of the thinner wire is 10 ohm, the resistance of

Fluorescent tubes are fitted with a choke. The choke coil:

Consider the following statements: An ordinary light bulb has a rather short life because the: 1. filament wire is not uniform. 2. bulb cannot be evac

Consider the following statements regarding a motor car battery: 1. The voltage is usually 12 V. 2. Electrolyte used is hydrochloric acid. 3. Electrod

A fuse is used in mains electric supply as a safety device. Which one of the following statements about the fuse is correct?

Which one of the following is paramagnetic in nature?