Genes are located in the chromosomes in the nucleus of the cell.

2x-y=9........ (i)
3x+y=0 ........ (ii)

add (i) and (ii), we get

5x = 9

x = 9/5

Put x = 9/5 in (ii) , we get
3(9/5) + y = 0

27/5 + y = 0

y = -27/5

• The heat energy which has to be supplied to change the state of a substance is called its latent heat.
• Latent heat does not raise (or increase) the temperature. But latent heat has always to be supplied to change the state of a substance .The word ‘latent’ means ‘hidden’.
• The latent heat which we supply is used up in overcoming the forces of attraction between the particles of substance during the change of state. Latent heat does not increase the kinetic energy of the particles of the substance, so the temperature of a substance does not rise during the change of state.

In 1774, Louis XVI, a 20 year young from Bourbon dynasty ascended the throne of France.
He was welcomed by empty treasure. The France was reeling under tremendous debt which had mounted Up to 2 billion livres.For meeting theses expenses increase in the tax was inevitable.

The French Society was divided into three estates. First two enjoyed all privileges.

1st Estate: Clergy
2nd Estate: Nobility
3rd Estate: Big businessmen, merchants, court officials, peasants, artisans, landless labourers, servants, etc.

• Some within the Third Estate were rich and some were poor.
• The burden of financing activities of the state through taxes was borne by the Third Estate alone.

Factors Affecting Climate Changes

• Topography: It means the shape of a land. Latitudes and elevation ranges are one of the factors that lead to fluctuation in surface temperatures. It can lead to local changes in climate.

• Sea level: Distance from the sea and nearby water bodies are one of the influential factors that affect the climate of a region. The surface temperatures in Sea have an effect on land temperatures. Coastal areas are cooler and wetter than internal areas. This leads to cloud formation when warm air from these interior areas meets cool air from the sea.

• Ocean currents: Ocean currents could transfer heat energy from land to sea or vice versa thus affecting the temperature of the region.

• Prevailing winds: Winds distribute particular air masses. The direction of the wind could determine the climate of a region. Since the wind from the humid region could bring cool air while that from the dry region would bring hot air.

Tatti se

It is the ability of an atom to gain or lose electron in order to achieve the noble gas configuration. It refers to the ability of an element to combine with other element. It is obtained by determining the number of electrons in the outermost shell (also called valence shell) of each atom of an element. For instance, sodium has 1 electron in its outermost shell and hence valency of sodium is 1.

(4a+3b)² - (4a-3b)² + 48ab

= (4a)² + (3b)² + 2(4a)(3b) + (4a)² + (3b)² - 2(4a)(3b)+ 48ab

= 16a² + 9b² + 24ab + 16a² + 9b² - 24ab + 48ab

= 16a² + 16a² + 9b² + 9b² + 48ab

= 32a² + 18b² + 48 ab

Parsec (pc)

1 pc = 3.08 x 10¹⁶ m

One parsec (pc) is the distance to a star that subtends and angle of 1 arc second at an arc length of 1 AU.

Parallax is “the best way to get distance in astronomy,” said Mark Reid, an astronomer at the Harvard Smithsonian Center for Astrophysics. He described parallax as the “gold standard” for measuring stellar distances because it does not involve physics; rather, it relies solely on geometry.

The Vernier calliper is used to measure the length or thickness of an object with great accuracy. It was invented by Pierre Vernier in 1630. It can measure length less than 1 mm.
A Vernier calliper consists of a fixed main scale or ordinary scale, a sliding Vernier scale, movable jaws, and a tail.
Parts of a Vernier Calipers

Main Scale: The main scale consists of a steel metallic strip graduated in centimeters at one edge and in inches at the other edge . It consists of a fixed external jaw and a fixed internal jaw.
Vernier Scale: A vernier scale  slides on the strip. It can be fixed in any position by the retainer. On the Vernier scale, 0.9 cm is divided into ten equal parts. It consisits of a fixed external jaw and a fixed internal jaw.

External Measuring Jaws: The outer measuring jaws (one of the main scale and the other of the vernier scale) helps to take the outer dimension of an object

Internal Measuring Jaws: The inner measuring jaws (one of the main scale and the other of the vernier scale) helps to take the inner dimension of an object.
Retainer: The retainer helps to retain the object within the jaws of the Vernier calipers to fix firmly.
Depth Measuring Strip: The depth measuring strip (prong) helps to measure the depth of an object. 

Least Count: The smallest length that can be measured accurately with a device is called the least count of that device. The least count of a Vernier calliper is known as the Vernier constant.

The least count or the smallest reading which you can get with the instrument can be calculated as:

Least Count = One main scale division - one Vernier scale division ------------ (i)

The greenhouse effect is the trapping of the sun's heat in the atmosphere of a planet by gases in that atmosphere. The green house effect happens because of so-called greenhouse gases, which includes carbon dioxide, methane, water vapor & other. The greenhouse effect is hugely significant.