Question Discussion & Solution

An electrician wears rubber gloves to avoid electric shock while repairing an electrical switch.

• As the human body is a good conductor of electricity.
• So it can pass through electricity from itself when it comes in contact with electricity and may get shocked or even fatality.
• As rubber is an insulator i.e. it is a non-conductor of electricity.
• So it protects the body of electricians from direct contact with electricity.

The correct answer is Deforestation.

• Deforestation is not related to conservation of land resources.

Key Points

• The felling and clearing of forest cover or tree plantations to accommodate agricultural, industrial or urban use is Deforestation.
• Deforestation can also be seen as removal of forests leading to several imbalances, both ecologically and environmentally.
• According to the Global Forest Resources Assessment 2020 (FRA 2020) report, the rate of forest loss has declined in the period of 1990-2020.
• The world’s total forest area is 4.06 billion hectares (bha), which is 31% of the total land area.

Additional Information

• The FRA is released by the United Nations Food and Agriculture Organization (FAO).
• Restriction on overgrazing is done to reduce Negative effects of grazing which include overgrazing, increased soil erosion, compaction and degradation, deforestation.
• Land reclamation is the process of creating new land from oceans, seas, riverbeds or lake beds.
• Regulated use of fertilizer controls the movement of water and nutrients within the plant.

The correct answer is 7.

Key Points

• The pH value of salts of strong acid and strong base is 7.
  • The salts are from a strong acid and strong base do not hydrolyze and the resulting salt pH will remain 7.
  • The anion in the salt form's strong base does not attract the H+ from the water.

Additional Information

• Salt of a strong acid and a weak base is acidic with a pH value less than 7 because acid is strong which retains the pH value less than 7.
• Salt of a weak acid and strong base is basic with a pH value of more than 7 because the base is strong hence pH of the whole solution will be more than 7.
• Salt of a strong acid and strong base is neutral because both are strong and cancels strong effects of each other, the pH will be 7.

The correct answer is Constellation.

• Ursa Major constellation lies in the northern sky. Its name means “the great bear,” or “the larger bear” in Latin.
• Ursa Major is the largest northern constellation and third largest constellation in the sky.
  • Its brightest stars form the Big Dipper asterism, one of the most recognizable shapes in the sky, also known as the Plough.
• Ursa Major contains seven Messier objects. It also contains 13 stars with confirmed planets.

Important Points

• The biggest known galaxy is IC 1101, which is 50 times the Milky Way's size and about 2,000 times more massive.
  • It is about 5.5 million light-years across.
• Our Sun (a star) and all the planets around it are part of a galaxy known as the Milky Way Galaxy.
  • A galaxy is a large group of stars, gas, and dust bound together by gravity. The Milky Way is made up of about 90% dark matter, the matter which cannot be seen, and about 10% “luminous matter”, or matter that we can see with our eyes.
  • The solar system lies about 30,000 light-years from the galactic centre.

Additional Information

• Sirius, also known as the Dog Star or Sirius A, is the brightest star in Earth's night sky.
• The name means "glowing" in Greek.

The correct answer is Copper and Tin.
Key Points

• Bronze
  • Bronze is an alloy traditionally composed of copper and tin.
  • Bronze is of exceptional historical interest and still finds wide applications.
  • It was made before 3000 BC, though its use in artifacts did not become common until much later.
  • The proportions of copper and tin varied widely (from 67 to 95 percent copper in surviving artifacts), but, by the Middle Ages in Europe, certain proportions were known to yield specific properties.
  • An alloy described in an 11th-century Greek manuscript in the library of St. Mark’s, Venice, cites a proportion of one pound copper to two ounces of tin (8 to 1), approximately that used for bronze gunmetal in later times.
  • Some modern bronzes contain no tin at all, substituting other metals such as aluminum, manganese, and even zinc.

Additional Information

• Copper and Silver
  • The best-known copper-silver alloy is sterling, which is 92.5 percent silver and 7.5 percent copper.
  • In England sterling, silver is traditionally identified by the hallmark of a lion passant.
  • Coin silver is an alloy of 90 percent silver and 10 percent copper.
  • For jewelry and ornaments, 85–90 percent silver (and the balance copper) is frequently used.
  • Dental alloys of 60–70 percent silver, 18–25 percent tin, 2–14 percent copper, and 0.5–2 percent zinc are amalgamated with varying quantities of mercury to form the filling materials for cavities in teeth.
• Copper and zinc
  • Brass is an alloy of copper and zinc, of historical and enduring importance because of its hardness and workability.
  • The earliest brass was called calamine brass, which dates to Neolithic times.
  • It was probably made by the reduction of mixtures of zinc ores and copper ores.
  • In ancient documents, such as the Bible, the term brass is often used to denote bronze, the alloy of copper with tin.
• Copper and Lead
  • Leaded bronzes contain from 4 to 25 percent lead plus additions of copper and tin, and some copper-lead bearing alloys contain up to 40 percent lead.
  • All these bearing alloys are sufficiently soft so that lubrication failure does not result in damage to the bearing.
  • Lead-based bearing alloys are also known as lead-based babbitt metals or white metals.
  • These are usually antimonial lead with widely variable additions of tin or copper (or both) and arsenic to increase strength.
  • One such alloy is commonly used for railroad-car journal bearings, contains 86 percent lead, 9 percent antimony, and 5 percent tin.
  • Many alloys of lead and alkaline-earth metals, such as calcium and sodium, also are widely used as bearing materials.