Give scientific reasons:

Question 12 Marks

Mustard seeds when shaken vigorously in a glass bottle stick to the sides of the bottle.

Answer

When seeds are shaken they get electrically charged and therefore they stick to the neutral walls of the glass.

Question 22 Marks

Repulsion is a test used for identifying an electrically charged object.

Answer

When a charged object is brought near a neutral object, it gets attracted when two oppositely charged objects are brought close, they get attracted. Therefore, attraction is not a test.
But when two like charges are brought close only then repulsion takes place.
Therefore, repulsion is the sure test for identifying an electrically charged object.

Question 32 Marks

It is dangerous to stand under a tree in rainy and stormy weather.

Answer

Large amount of charges get built up in the clouds in rainy and storming weather.
Sometimes these charges are transferred to the earth in the form of a bolt of lightning.
Generally lightning strikes tall buildings and trees. If lightning strikes a tree then either the tree may fall or it may catch fire.
In both cases this would be dangerous for anyone standing under the tree, hence it is dangerous to stand under a tree in rainy and stormy weather.

Question 42 Marks

High rise buildings have lightning conductors.

Answer

High rise buildings are prone to lightning strikes during the monsoon.
When lightning strikes, a tremendous electric charge is transferred to the earth, which may damage the tall buildings.
To prevent this, high rise buildings have a forked metal rod, called a lightning conductor fitted on the top of the building.
The lower end of this rod is buried inside the earth.
If lightening strikes, the electric charge passes through this conductor and goes in to the earth. In this way the building is saved from damage.

Question 52 Marks

Charge cannot be developed on a copper rod.

Answer

Charge cannot be developed on a copper rod because only certain pairs of substances give rise to electric charge, on rubbing.

Question 62 Marks

Ordinarily, an atom does not have any charge.

Answer

Every atom contains smaller particles with either positive or negative charge.
As the number of positively and negatively charged particles in an atom is equal, they neutralize each other.
As a result the atom has no charge.

Science Give scientific reasons: