Question Discussion & Solution

CONCEPT:

• Electric Power: The rate at which electrical energy is dissipated into other forms of energy is called electrical power i.e.,

\(P = \frac{W}{t} = VI = {I^2}R = \frac{{{V^2}}}{R}\)

Where V = Potential difference, R = Resistance and I = current.

EXPLANATION:

• Mathematically power can be written as,

\(\Rightarrow P = \frac{W}{t} = VI \)

If, W = 1 J and t = 1 sec, then P = 1 watt

• Thus the power of an electric circuit is said to be one watt or 1 ampere - volt if one joule of energy is consumed in one second. Therefore option 1 is correct.

The correct answer is Curvature of the lens.

Important Points

• Focal length of a lens depends on its curvature and the medium outside the lens.

Additional Information

• The ability of a lens to converge or diverge light rays depends on its focal length.
  • For example, a convex lens of short focal length bends the light rays through large angles, by focussing them closer to the optical centre.
  • Similarly, the concave lens of a very short focal length causes a higher divergence than the one with a longer focal length.
• The degree of convergence or divergence of light rays achieved by a lens is expressed in terms of its power.
  • The power of a lens is defined as the reciprocal of its focal length.

Explanation:

Option 1 is correct, i.e. Anthracite.

• Anthracite, also called the hard coal is a highly metamorphosed form of coal.
• The calorific value of a substance is defined as the amount of heat released by a unit weight of a substance during complete combustion.
• Anthracite coal has the highest calorific value.

Anthracite is a type of coal that has the highest carbon content.

• Anthracite: 87-96%
• Bituminous: 45-86%
• Lignite: 25 - 35%

Extra information:​

• The most common volatile matter in coal is water, carbon dioxide, and sulfur dioxide.
•  Volatile matter is directly related to coal rank; as coal rank increases, volatile matter content decreases.
• Peat has the highest volatile matter.

The correct answer is China.

Key Points

• The Russia and China joint naval exercises “Joint Sea 2021” has kicked off at Russia’s Peter the Great Gulf, in the Sea of Japan, on October 14, 2021.
• The exercises will culminate on October 17, 2021.
• The drill is being carried out as part of ‘Joint Sea’ 2021, the series of bilateral naval exercises that have been taking place between the two services since 2012.

Additional Information

•  Important Exercises between India and other countries:

Inheritance

The capability of a class to derive properties from another class is called Inheritance

• The class that inherits properties from another class is called Subclass or Derived Class.
• The class whose properties are inherited by a subclass is called Base Class or Superclass.

Syntax for Inheritance

class derived_name : access_mode base_class

{

//body of derived class

};

Additional Information 

Polymorphism

Polymorphism is mainly divided into two types:

• Compile-time Polymorphism
• Runtime Polymorphism

Compile-time polymorphism

This is achieved by function overloading or operator overloading.

• Function Overloading - When there are multiple functions with the same name but different parameters then these functions are said to be overloaded
• Operator overloading - When there are multiple operations can be performed by using single operator is called operator overloading for example operator ‘+’ when placed between integer operands, adds them and when placed between string operands, concatenates them

Run Time Polymorphism

It is achieved by Function Overriding.

Conclusion

Feature of Reusability is followed by inheritance so the correct answer is the inheritance.