Q61. Bakelite is used for making electrical appliances because it is a
(a) thermoplastic
(b) good conductor of heat
(c) good conductor of electricity
(d) good insulator of electricity
Answer: (d) good insulator of electricity
Explain: Bakelite is a thermosetting plastic. It is used as an insulator in electric appliances because it is a poor conductor of electricity.
Q62. In which of the following cases of motion is the distance moved and the magnitude of displacement equal?
(a) A car moving on a straight road
(b) A car moving in a circular path
(c) A pendulum oscillating to and fro
(d) The Earth revolving around the Sun
Answer: (a) A car moving on a straight road
Explain: The distance traveled by a body is equal to the magnitude of displacement only when the body follows the shortest distance (traveling in a straight line) between its initial and final position.
Q63. LED and CFL are very commonly used as sources of light in homes. Which of the following statements is true?
(a) CFL is better because LED contains toxic materials
(b) LED is better because CFL contains toxic materials
(c) Both are equally good
(d) Neither of them is good because both contain toxic materials
Answer: (b) LED is better because CFL contains toxic materials
Explain: LED is energy-efficient and more environment-friendly than CFL because it does not contain mercury (toxic substance) which is found in CFL.
Q64. An air bubble inside water behaves like a
(a) concave lens
(b) convex lens
(c) Plano-convex lens
(d) concave mirror
Answer: (a) concave lens
Explain: An air bubble in water would behave as a concave lens (diverging lens). This can be observed by passing a ray of light through the air bubble. The light entering into the bubble would spread out or diverge. In the case of the convex lens, the light rays converge to meet at a single point.
Q65. A feather weighing 5 gm and a nail weighing 10 gm have the same kinetic energy. Which of the following statements is true about the momentum of two bodies?
(a) The lighter body will have higher momentum
(b) The heavier body will have higher momentum
(c) Both will have equal momentum
(d) It is not possible to compare the momentum of two objects
Answer: (b) The heavier body will have higher momentum
Explain: Momentum is a vector measurement. It is directly proportional to the mass and velocity of the object. t is calculated by the following formula:
Momentum (P)= Mass x Velocity
So, it is clear that the momentum of heavier bodies will be more.
Q66. If the pressure over a liquid increase, its boiling point
(a) decreases
(b) increases
(c) does not change
(d) first decreases and then increases
Answer: (b) increases
Explain: The boiling point of a liquid is the temperature at which the pressure of the gas (air pressure) is equal to the vapor pressure of the liquid. The boiling point of the liquid is directly influenced by the pressure over the liquid. If the external pressure is less than 1 atmosphere, then the boiling point of the liquid would be less than its normal boiling point. Similarly, if the pressure is more than 1 atmosphere, then the boiling point of the liquid would be more than its normal boiling point.
Q67. A doctor prescribes a medicine to treat hyperacidity. The main ingredient of the medicine is
(a) Al(OH)3
(b) MgCl2
(c) CaCO3
(d) Na2CO3
Answer: (a) Al(OH)3
Explain: Aluminum hydroxide is an antacid that reacts with the excessive acid secreted in the stomach; thereby, reducing the acidity. Thus, t IS used in the medicines of hyperacidity.
Q68. Non-metallic oxides
(a) are acidic in nature
(b) are basic in nature
(c) are amphoteric in nature
(d) turn red litmus paper blue
Answer: (a) are acidic in nature
Explain: Non-metallic oxides are acidic in nature; thus, they turn the blue litmus red. The metallic oxides are amphoteric, i.e., they can react as acid as well as a base.
Q69. The inner surfaces of food cans are coated with tin and not with zinc because
(a) zinc is costlier than tin
(b) zinc is more reactive than tin
(c) zinc has a higher melting point than tin
(d) zinc is less reactive than tin
Answer: (b) zinc is more reactive than tin
Explain: The more reactive elements are generally not used for coating food storing utensils because they can easily react to coming in contact with air. Tin being less reactive than Zinc and iron is used for coating the iron cans to prevent corrosion.
Q70. Man goes door to door posing as a goldsmith. He promises to bring back the glitter on dull gold ornaments. An unsuspecting woman gives a set of gold bangles to him which he dips in a particular solution. The bangles sparkle but their weight has considerably reduced. The solution used by the impostor probably is
(a) dil. HCI
(b) conc. HCI
(c) a mixture of conc. HCl and conc. HNO3
(d) Conc. HNO3
Answer: (c) a mixture of conc. HCl and conc. HNO3
Explain: Aqua regia refers to the mixture of conc. HCI and conc. HNO3 mixed in a ratio of 3:1. It is a highly corrosive and fuming fluid which has the capacity to dissolve gold and platinum. None of the liquids can do this alone. Since the outer layer of gold on the bangles was dissolved in aqua regia, the weight of bangles got reduced.
