8 –
Static Electricity
Q
1.Choose the correct option and fill in the blanks :
(always repulsion, always attraction, displacement of
negative charge, displacement of positive charge, atom, molecule, steel,
copper, plastic, inflated balloon, charged object, gold)
(1) There is ...................... between like charges.
(2) ..................... is responsible for generation
of electric charge in an object.
(3) A lightning conductor is made of a
..................... strip.
(4) ..................... does not get electrically
charged easily by rubbing.
(5) There is ..................... when opposite electric
charges come near each other.
(6) A ................... can be detected with an
electroscope.
Ans.
(1) always repulsion (2) Displacement of negative charge (3) Copper 4) Plastic
(5) always attraction (6) charged object
Q. 2. Answer the following questions in one sentence :
(1) How will you
protect yourself from lightning?
Ans. In order to protect oneself, the shelter
should be taken in a house that has lightning conductor
(2) How are charges generated?
Ans. When two objects are rubbed against each
other, the negative charge on one of the object is transferred to other object.
Making the second object to acquire negative charge. The first object becomes
positively charged due to loss of negative charge.
(3) In the
lightning conductor, what provision is made for spreading the electricity into the ground?
Ans. [1] Lightning
conductor consists of a long copper strip, one end of this is forked. The
forked end is placed at the highest part of the building. [2] the other end of
the strip is connected to a plate of cast iron. [3] In a pit dug in the ground,
coal and salt are filled. The iron plate is placed upright in the pit. [4] Some
provision is also done to pour water into it. This is to help in spreading the
electric charge quickly into the ground and prevent damage.
(4) Why do farmers
stick an iron staff into the ground while working in the field in rainy
conditions?
Ans. An iron staff works like a lightning
conductor. Working of the lightning
conductor: (1) The lightning conductor is a device used for protection
from a lightning strike. (2) Whenever an electrically charged cloud passes over
the builiding, the electric charges try to flow towards the building due to
difference in their charge (3) Clouds have the negative charge, while the
building has a positive charge.(4) The force of attraction thus acts and the
lightning may fall down on the building. (5) But these currents are conducted
into the ground through the copper strip of lightning conductor. The damage to
the building is thus prevented. (6) When such a lightning conductor earthing
fixed on a tall building, the surrounding area is also protected from
lightning.
(5) Why is lightning not seen every day
during the rainy season?
Ans. When there is electric charge produced
on a very large scale, then only there is possibility of lightning. Rest of the
times such condition may not be there. Therefore, lightning is not seen every
day during the rainy season.
Q 3. Explain why it is not safe to go out
with an umbrella when there is heavy rain, lightning and thunder.
Ans. Generally the central rod of an umbrella
is metallic with a pointed tip at the upper extremity. Moreover, the ribs of
umbrella are also made up of metals. When there is heavy rain along with
lightning and thunder, the lightning strike can be attracted towards the umbrella.
This attraction is between the opposite charges on the cloud and the umbrella. since
our body is a good conductor of electricity, we may get a forceful shock. This
can be lethal too. In order to avoid such a hazard, it is not safe to go out
with an umbrella when there is heavy rain.
Q 4. What are the characteristics of a static
electric charge?
Ans.
Characteristics of static electric charge : (1) The charge is developed only where
friction occurs. (2) The charge developed after rubbing two unlike objects is
equal and of different types. (i.e. positive and negative). The combined total
of both the charges is zero (3) The static electric charge is of short
duration.
(10) What is the damage caused by lightning?
How will you create awareness to prevent it?
Ans.
(1) Damage caused by lightning : There is great damage to the trees,
building etc. The trees burn and the property
is destroyed. The electrical equipments in the house become useless. (2)
Awareness to prevent damage : One should not move out of the house when there
is thunder and lightning. People should be made aware about the safety during such times They should not go into the water.
One should not stand under a tree or go to the open spaces and heights. The
lightning conductors should be installed in all buildings. The disaster
management should be known to people.
