Q1. Why does a plastic comb rubbed with dry hair attract tiny pieces of paper?
a) Charging by rubbing: Charging of an object by rubbing it with another object is calledcharging by rubbing. c) Charging by induction: Charging a neutral body by bringing it near a charged body is called charging by induction. If the divergence of the leaves increases, the body has similar charge that is the given body is also negatively charged. If the divergence of the leaves decreases, the body has unlike charge that is the given body is positively charged. Q11. What will you observe when the metal cap of an electroscope is touched with a plastic comb rubbed in dry hair? Give reason for your answer.
Ans:Tremors or vibrations caused by the earthquakes which travel in the form of waves within the earth or along the earth's surface, are called seismic waves. Seismograph is an instrument which records these waves.
Ans: Two places in India which are most threatened by earthquake are 1. Kashmir 2. Rann of kutch. Ans: The earth's lithosphere is fragmented into many pieces. Each fragment is called a plate, also called tectonic plate. These plates are in continuous motion i.e. they float over hot magma.
Ans: Lightning conductor is a device used to protect buildings from the damaging effects of lightning. It runs from the top to the bottom, along the outer wall of the buildings or any other object, which is to be protected. If lightning strikes the buildings or any other objects, then the lightning conductor provides an easy and direct path for the lighning bolt to pass to the ground without effecting them. Ans: The process of transferring of charge from a charged object to the earth is called earthing. For our safety, most of the electrical appliances and the mains of the house are connected to earth, so that we can be prevented from getting an electric shock.
23. We can easily charge non-metals like rubber, woollen clothes, plastics, etc. whereas we cannot charge a copper rod by rubbing easily. Why?
Ans: When the metallic rods like copper rod are rubbed, charges does not build on their surface because charges can escape through metals as they are conductors whereas when non-metals like rubber, woollen clothes, plastics, etc. are rubbed, charges will build up on their surface because charges are not conducted through them as they are insulators. Ans: During the development of thunderstorm, air currents move in the upward direction and the water droplets move in the downward direction. These movements causes the seperation of charges. Usually, the negative charges accumulate at the lower part of the clouds and the positive charges are accumulated at its upper part. The positive charges are also accumulated at the ground also. When the accumulation of charges becomes large, a high potential difference is set up between lower part of clouds and earth, which is sufficient to break the insulation of air. As a result, negative and positive charges meet, producing streaks of bright light and sound. This process is called an electric discharge. Ans: An electroscope is used to detect the charge on a body. A plastic comp is taken and it is rubbed on hair. Now, the plastic comb gets charged. The comb is touched with the electroscope plate. The static charges which are developed on the comb travels down the conducting wire and reach the two leaves of aluminium foil. Similar charges are acquired by both the leaves and as a result, they repel each other. Thus, the method of charging an uncharged body by bringing another charged body directly in contact is called charging by conduction. Hence, by this way, an electroscope can be charged through conduction.
8 Comments
alisha
7/3/2015 08:14:37 am
Wow it helped me a lot ...
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nikhil
13/2/2017 04:47:29 pm
me too
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Adithi
27/2/2016 07:12:51 am
It s informative.....thank u
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Abhijeet singh chouhan
3/3/2016 07:56:26 pm
Thanksfor the answers
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simran
24/12/2016 09:33:58 am
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Shraban Nee
5/3/2017 10:17:38 am
Useful
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Sairam
31/12/2017 07:14:56 pm
it was so easy to understand the whole lesson after reading these answers . so thank u
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