Question Discussion & Solution

The correct answer is four.

Key Points

• Crocodiles have four-chamber hearts. All reptiles have incomplete four-chamber hearts except Crocodiles.

Additional Information

• Endotherm or Homeotherm have well developed four-chamber heart. Examples:- Birds and mammals. 
  • They can maintain constant body temperature.
• Poikilotherm or Ectotherm do not have a well-developed heart, so they can not maintain constant body temperature. Examples:- Amphibians and reptiles.
• Fishes have a two-chamber heart.
• Amphibians have three-chamber heart.
• The cockroach has thirteen chamber hearts.

​The correct answer is Truck farming.

Key Points

• The farmers specialize in vegetables only, this type of farming is known as Truck farming.
• In the regions where farmers specialize in vegetables only, the farming is known as Truck farming, and the distance of truck farms from the market is governed by the distance that a truck can cover overnight, hence the name truck farming.
• Vegetable farms are in some regions known as truck farms: "truck" is a noun for which its more common meaning overshadows its historically separate use as a term for "vegetables are grown for the market".
• The production of crops of some vegetables on an extensive scale in regions especially suited to their culture primarily for shipment to distant markets known as Truck farming.
• The major truck-farming areas are in California, Texas, Florida, along the Atlantic Coastal Plain, and in the Great Lakes area.
• Centres for specific crops vary with the season. Among the most important truck crops are tomatoes, lettuce, melons, beets, broccoli, celery, radishes, onions, cabbage, and strawberries.

Additional Information

Joule is the SI unit of Energy.

Similarly,

Pascal is the SI unit of pressure.

Hence, pressure is the correct answer.

Additional Information 

* S.I Unit of Resistance is the Ohm.

* S.I Unit of Energy is Joule.

* S.I Unit of Volume is the Cubic meter.

* S.I Unit of Force is Newton.

* S.I Unit of Area is the Square meter.

* S.I Unit of Temperature is Kelvin.
Important Points 

There is a total of 9 S.I units.

1. 7 of them are fundamental units.

2. 2 of them are Supplementary units.

• Apiculture is the technique of scientific rearing of honey bees in a specially designed wooden box.
• The essential elements for beekeeping are smoker, safety dress, moveable hive, honey extractor and hive tool.
• Sericulture is the process of rearing of silkworms to produce raw silk.
• Sericulture is the production of raw silk by means of raising caterpillars (larvae), those of the domesticated silkworm.
• Silk is a continuous filament within each cocoon.

Additional Information

Concept:

• Atoms are made up of subatomic particles - electrons protons and neutrons.
• In the center of an atom, a nucleus is present which contains protons and neutrons together known as nucleons.
• The mass of an atom is most concentrated at the center of the atom, i.e. the nucleus.

​Electrons:

• Discovered by Sir J.J Thomson in the year 1897.
• Previously named as cathode rays as they were supposed to be emitted from the cathode.
• They are deflected towards the positive side.
• They have high kinetic energy.
• They are deflected by an electric and magnetic field.
• It has a negative charge of

  \(charge=1.602\times10^{-19} coulombs \)
\(mass={1\over 1837}\times 9.107\times 10^{-28}g\)

Protons:

• Discovered by Goldstein.
• Depicted first as positive rays because it seemed to emerge from the anode.
• Mass of a proton is

 \(1.670 \times 10^{- 24}g\)

\(Charge=1.602\times 10^{-19} coulombs\)​

Explanation:

• Rutherford's discovery led to the discovery of nucleus.
• He found out that most of the mass of the nucleus is situated in its centre and contains the positively charged particles protons.
• The atom is otherwise empty and as electrons have negligible mass, the mass of an atom should be equal to the sum of mass of protons present in it.
• However, it was seen that in Helium, there are only two protons, so its mass should be twice the mass of each proton = \(2\times 1.008 a.m.u\).
• Experimental results revealed that it has a mass of 4.003a.m.u.
• Hence, it was concluded that the nucleus has particles containing no charge but mass almost equal to that of a proton.
• This was established by scientist James chadwick in 1932.

Additional Information

Rutherford's gold foil experiment: 

• He discovered the atomic nucleus and gave us an atomic model.
• He directed alpha particles towards a metal sheet.
• He saw that most of the alpha particles, which are positively charged particles, are not getting deflected.
• Most of the alpha particles emerged undeflected.

• Therefore, he concluded that most of the mass of the nucleus is situated in its centre and contains the positively charged particles protons.
• Electrons revolve around the nucleus in certain orbits.