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# Tag Archives: Earth Sciences

## Sample Value based questions for Class 12 Physics

Scientific and logical reasoning is a scientific value expected from students studying Physics. Use your expertise to answer the following question.
One way to make a compass is to stick a magnetized needle into a piece of cork and float it in a glass bowl full of water. The needle will align itself with the magnetic field of the earth. Since the north pole of the needle is attracted towards the north, will the needle float towards the northern side of the bowl? Defend your answer.

Mr. Kishan is a farmer who was staying happily in a hut made of hey and
leafy roof. It is easy for him to renovate his home with new leaves every
year as the good quality palm leaves he get free of cost and it is
environment friendly. Most of the village people are satisfied with the
same type of huts there.
But one day during heavy lightning, many of the huts were burnt to ashes
and people were sad and disappointed. Mr. Sekhar works in electricity
department and has good knowledge of current affairs. He soon reached
the spot along with his friends and pacified them and made arrangements
for their comfortable stay. The very next day the team could erect many
lightning conductors and few cavities of metal conductors and made
awareness to the villagers about lightning and the use of things installed
there. (a) What according to you, are the values displayed by Mr. Sekhar
and his friends to help Mr. Kishan and the village people? (2)
What is the principle behind working of a lightning conductor? Also by
applying Gauss theorem show that net electric field inside the metallic
cavity is zero. (2)

## How does the atmosphere rotate with the Earth?

How does the atmosphere rotate with the Earth? (Asked George)

## Variation in acceleration due to gravity (g) with depth

As we go deeper from the earth suface the gravity starts decreasing but formulla is ‘F=G*m*M/r2 where distance between the object and the earth is r2 which is inversally proportional to the ‘g’ then why as we go deeper from the earth suface the gravity starts decreasing; it should be increased because distance between the earth and the object is less. but it start decreasing why?

When we go deeper into earth, the attraction at that point is due to a sphere of earth of radius (R – d) where d is the depth below the surface of earth.

Let a body of mass m be kept on the surface of earth. The force exerted by earth on it,

$F_{surface}=mg=\frac{GMm}{R^{2}}$ where M is the total mass of earth and R is the radius of earth.

But, $M&space;=&space;\frac{4\pi&space;R^{3}\rho&space;}{3}$

Substituting for M,

$mg&space;=&space;\frac{4\pi&space;G\rho&space;m&space;R}{3}$

or  (more…)

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