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Science [2 Mark Questions]

Electricity. · Tamil Nadu Board STD 8 (Tamil - English Medium). 10 questions.

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[2 Mark Questions]

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10 questions · timed · auto-graded

Question 12 Marks
You might have observed on a dry day that when you touch the screen of a television you get a slight shock. Why does it happen?
Answer
It happens because the television screen is charged and have static charges and when we touch with our hands which are uncharged, the charges attract our hands and transfer through our hands and we get a small shock.
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Question 22 Marks
During lightning and thunder we should avoid standing in ground and open spaces Why?
Answer
During lightning and thunder, we should avoid standing in ground and open spaces. You should make yourself as small as possible by squating. It is however safe to stay inside a car because the car acts as a shield and protects us from the electric field generated by the storm.
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Question 32 Marks
During the construction of a building, the lightning conductor was left hanging in the air by mistake will it be effective? Explain.
Answer
Lighting conductor will not work. It left hanging in the air because in order to work, it must be installed properly and grounded using copper plate.
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Question 42 Marks
Give some uses of electroplating.
Answer
Electroplating is applied in many fields:
  1. We use iron in bridges and automobiles to provide strength.
  2. A coating of zinc is deposited on iron to protect it from corrosion and the formation of rust.
  3. Chromium has a shiny appearance. It does not corrode.
  4. It resists scratches.
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Question 52 Marks
How charges are produced by friction?
Answer
Rubbing certain materials with one another can cause the build-up of electrical charges on the surfaces. So charges are produced by friction.
Example:
Combing hair charges are transferred from the hair to the comb due to friction.
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Question 62 Marks
Give a reason for the following.
One should not use an umbrella while crossing an open field during thunderstorm.
Answer
Reason:
  1. Carrying an umbrella is not advisable during a thunderstorm.
  2. As the rod of the umbrella and its supporting wires are made up of metals.
  3. Thus during a thunderstorm, the conducting object should be avoided.
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Question 72 Marks
Give a reason for the following.
In an electroscope, the connecting rod and the leaves are all metals.
Answer
Reason:
These are made of metals so that the electrons become free to move.
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Question 82 Marks
Give a reason for the following
When you touch the metal disc of an electroscope with a charged glass rod the metal leaves get diverged.
Answer
Reason:
The leaves of an electroscope diverge because when a glass rod is touched on the metal disc, the charge travels through the metal rod to the leaves. Since, like charge repel, the charge travels till the leaves and then opens up as both the leaves have like charges.
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Question 92 Marks
Give a reason for the following.
When a comb is rubbed with dry hair it attracts small bits of paper.
Answer
Reason:
Comb rubbed with hair gains electrons from the hair and becomes negatively charged. These electrons are accumulated on the surface of the comb. When a piece of paper is torn into bits, positive and negative charges are present at the edges of the bits. Negative charges in the comb attract positive charges in the bits. So, the paper bits are moving towards the comb.
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Question 102 Marks
Give a reason for the following.
When a glass rod is rubbed with silk cloth both get charged.
Answer
Reason:
When a glass rod is rubbed with a silk cloth the free electrons in the glass rod are transferred to the silk cloth. It is because the free electrons in the glass rod are less tightly bound as compared to that in silk cloth. Since the glass rod loses electrons, it has a deficiency of electrons and hence acquires a positive charge. But, the silk cloth has an excess of electrons. So, it becomes negatively charged.
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[2 Mark Questions] - Science STD 8 Questions - Vidyadip