Q274. 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 supplied is 50 Hz.

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): The temperature of a metal wire rises when an electric current is passed through it. Reason (R): Collision of metal atoms with each other release

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): 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

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

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): According to statistics, more female children are born each year than male children in India. Reason (R) : In India, the death rate of a male chi

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) : 60° - 65° latitudes in both the hemispheres have a low pressure belt instead of high pressure. Reason (R) : The low pressure areas are permanent

Assertion (A) : The same face of the moon is always presented to the earth. Reason (R) : The moon rotates about its own axis in 23 and half days which is about

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

Assertion (A): In human body, liver has important role in fat digestion. Reason (R): Liver produces two important fat-digesting enzymes.

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

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): A man standing on a completely frictionless surface can propel himself by whistling. Reason (R): If no external force acts on a system, its momen

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?