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Correct option  (4)  a > b > d > c

Explanation:

The S_N1 reaction is proportional to stability of carbocation formed in the rate determining step.

Correct option (4) (B) < (A) < (C) < (D)

Explanation:

Rate of S_N1– reaction ∝ stability of C^⊕– I.m

b). Both assertion and reason are true, but reason is not the correct explanation of assertion

a). Both assertion and reason are true, and reason is the correct explanation of assertion.

d). Both assertion and reason are false.

When ethyne is burnt in air, incomplete burning takes place and produce sooty flame due to limited supply of oxygen present in the air. However, if ethyne is burnt in oxygen, it gives a clean flame with high temperature (3000˚C) due to complete combustion of ethyne. Hence, this oxy-acetylene flame is used for welding and it is not possible to attain such a high temperature with air. Due to this reason, a mixture of ethyne and air is not used for welding.

When ester is treated with an alkali, the reaction gives ethanol and sodium ethanoate. This reaction is called saponification reaction because this reaction forms the basis of preparation of soap. 

This can be given by following equation: 

CH₃COOC₂H₅ + NaOH → CH₃COONa+C₂H₅0H

Correct option: (2) (i) - B, (ii) - D, (iii) - B, (iv) - A

Correct option: (1) Global warming

 (d) Distance

Explanation:

Light year is unit of distance  i.e. distance travelled in one year at the speed of light   

Correct option (4) R = r 

Explanation:

For maximum power transfer

R = r

The correct option (1) BeX₂  

Explanation:

According to fajan's rule when size of cation decrease, then covalent character increase. so BeX₂ is covalent in nature.

Answer is (2) 11/16

AA + ABA + BAA + ABBA + BBAA + BABA

= 1/4 + 1/8 + 1/8 + 1/8 + 1/16 + 1/16 + 1/16 = 11/16

Soap is basic in nature and hence turns red litmus blue.

Explanation:

Concrete Sleeper:

(i) Concrete sleeper is a kind of railway sleeper made of steel-reinforced concrete. With the characteristic of water-resistant, sun-resistant, and corrosion-resistant.

(ii) Concrete sleeper has been widely used all over the world since 1950.

Advantages of Concrete Sleepers:

• It is more durable having greater life (up to 50 years)
• It is economical as compared to wood and steel.
• Concrete sleepers can generally be mass-produced using local resources.
• Easy to manufacture.
• It is not susceptible to vermin attack
• It is not susceptible to fire
• Good for track circuited areas

Disadvantages of Concrete Sleepers

• It is brittle and cracks without warning.
• It cannot be repaired and required replacement.
• Fittings required are greater in number.
• No scrap value​

Advantages of Wooden Sleepers:

• They are cheap and easy to manufacture
• They are easy to handle without damage
• They are more suitable for all types of ballast
• They absorb shocks and vibrations better than other types of sleepers.
• Ideal for track circuited sections
• Fittings are few and simple in design
• Good resilience
• Ease of handling
• Adaptability to non-standard situation
• Electrical insulation

Disadvantages of Wooden Sleepers:

• They are easily liable to attack by vermin and weather
• They are susceptible to fire
• It is difficult to maintain gauge in the case of wooden sleepers
• The scrap value is negligible
• Their useful life is short about 12 to 15 years.

Advantages of Steel Sleepers:

• It is more durable. Its life is about 35 years
• Lesser damage during handling and transport
• It is not susceptible to vermin attack
• It is not susceptible to fire
• Its scrap value is very good

Disadvantages of Steel Sleepers:

• It is liable to corrosion.
• Not suitable for track circuiting
• It can be used only for rails for which it is manufactured
• Cracks at rail seats develop during the service.
• Fittings required are greater in number

Advantages of Cast Iron Sleepers:

• Service life is very long
• Less liable to corrosion
• Form good track for light traffic up to 110 kmph as they form rigid track subjected to vibrations under moving loads without any damping
• Scrap value is high

Disadvantages of Cast Iron Sleepers:

• Gauge maintenance is difficult as tie bars get bent up
• Not suitable for circuited track
• Need a large number of fittings
• Suitable only for stone ballast
• Heavy traffic and high speeds (>110kmph) will cause loosening of keys and development of high creep

Explanation:

Railway Gauge:

(i) The clear horizontal distance between the inner faces of the two rails forming a track is known as a Railway Gauge.

(ii) The distance between the inner faces of a pair of wheels is called the wheel gauge.

Types of Gauges in India

In India the following gauges are used:

• Standard Gauge or Broad Gauge: Gauge width 1.676 m.
• Metre/Meter Gauge (M.G): Gauge width 1.000 m.
• Narrow Gauge (N.G): Gauge width 0.672 m.
• Feeder Track Gauge or Light Gauge: Gauge width 0.610 m.

Advantages of Uniform Gauge:

The use of a uniform gauge has the following advantages:

• The delay cost and hardship in shifting passengers and goods from the vehicle of one gauge to the other are avoided.  
• Labour expenses of shifting are saved.  
• Breakage of goods due to shifting is avoided.  
• The possibility of thefts and misplacement during the shifting operation is eliminated.  
• Large sheds to store goods are not required.  
• Labour strikes etc. do not affect the service and operation of trains.   
• Wagons can be efficiently used on all the tracks if the gauge is uniform.  
• Locomotives can be effectively used on all the tracks if a uniform gauge is adopted.  
• During military movement, no time is wasted in shifting personnel and equipment if the gauge is uniform.  
• Duplication of equipment such as platforms, sanitary arrangements, etc is avoided.  

Factors Affecting Adopting of a Particular Gauge

The following factors govern the choice of different gauges:

• Cost of construction and funds available for the railway project.
• Volume and nature of traffic. 
• The intensity of the population.
• Industrial and commercial development of the locality.
• Prospects of future development of the area.
• Topographical and geological features of the country.
• Speed of movement required.

Explanation:

Track modulus:

(i) Track modulus is the index for stiffness or resistance to deformation of the permanent way. It is defined as the load per unit length of the rail required to produce unit deformation or depression in the track.

(ii) It depends on gauge distance, type of rails, type and density of sleepers and type of Ballast etc.

(iii) For computation of track modulus initial load taken for BG is 4 tonnes and for MG track is 3 tonnes. 

Explanation:

Load Determination in the designing of bridge or culvert:

(i) 

(ii) Dead loads include the weight of the bridge itself plus any other permanent object affixed to the bridge, such as toll booths, highway signs, guardrails, gates or a concrete road surface.

(iii) Live loads are temporary loads that act on a bridge, such as cars, trucks, trains or pedestrians.

(iv) Environmental loads are temporary loads that act on a bridge and that are due to weather or other environmental influences, such as wind from hurricanes, tornadoes or high gusts, snow, and earthquakes. Rainwater collecting might also be a factor if proper drainage is not provided.

Machine load is not consider in the designing of Bridges. 
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Explanation:

Steam engine: The heat engine that converts heat energy of steam into mechanical energy to perform many works is called a steam engine.

Internal combustion engine: An engine that converts chemical energy into mechanical energy by combustion of a fuel and generates mechanical power.

Internal combustion engine:

• The combustion of fuel takes place inside the engine cylinder.
• It has a noisy operation.
• The working pressure and temperature inside the engine are very high.
• It does not require a boiler and other components for energy transfer, therefore it is light and compact.
• It has a thermal efficiency of 30 to 35 %.
• It can start instantaneously.

Explanation:

Substitution Method:

It is a measurement technique in which the quantity is measured by direct comparison on an indicating device by replacing the measurable quantity with another which produces the same effect on the indicating device.
The substitution method is the algebraic method to solve simultaneous linear equations. As the word says, in this method, the value of one variable from one equation is substituted in the other equation. In this way, a pair of the linear equation gets transformed into one linear equation with only one variable, which can then easily be solved. 

Substitution Method Steps:
For instance, the system of two equations with two unknown values, the solution can be obtained by using the below steps. Here, the list of steps is provided to solve the linear equation. They are

• Simplify the given equation by expanding the parenthesis
• Solve one of the equations for either x or y
• Substitute the step 2 solution in the other equation
• Now solve the new equation obtained using elementary arithmetic operations
• Finally, solve the equation to find the value of the second variable

(a) For a thin prism, D = (μ – 1) A Since λ_b < λ_r ⇒ μ_r < μ_b ⇒ D₁ < D₂

In an electric circuit, the direction of flow of electron is taken to be from negative to positive but the direction of current (say conventional current) is taken from positive to negative. 

When electricity was discovered, scientists at that time were not aware of electrons. They thought that positive ions were responsible for conduction of current. Therefore, they decided that the direction of current would be from positive to negative. We still respect this convention even today. so we named it conventional current direction.

The great scientist J. J. Thomson when discovered electrons. Then everyone soon understood that electrons were responsible for current in most conductors. to change the previous convention was not a good idea. Hence, we continued to use the same convention.

|E| = |Φ_B|/ t

Where E is induced emf and Φ_B = BA cos α
Here B is magnetic field and A is area and α is the angle between circular wire plane and magnetic field.

Here α = 90°
So induced emf = 0 as cosα = 0

The correct answer is 1998.

• The India-Sri Lanka Commercial-Free Trade Agreement was signed in 1998.

• The commercial relations between Sri Lanka and India has marked a historical milestone when it was signed the India-Sri Lanka Free Trade Agreement (ISFTA) on 28^th December 1998, as the 01st bilateral free trade agreement of Sri Lanka.
• The ISFTA entered into force with effect from 01^st March 2000.
• The ISFTA is now in full implementation as both sides have completed their phasing out commitments under the respective Tariff Liberalization Programme (TLP).

• In 2011-12, India’s imports from Sri Lanka went up by almost 45% to cross US$ 720 million, making Sri Lanka the largest source of merchandise from the South Asian region for India.
  • This is a big jump from US$ 45 million imports in 2000-01 when Sri Lanka occupied 4^th rank as an import source for India in the region. 

(b) Finance Bill 

(a) vote on account

(c) appropriation bill

Allocation of resources is considered as inefficient when economy performs below the PPC curve.

In the electrolysis of alumina, cryolite is added to Lower the m.p. of alumina