Following examples show that the friction produces heat:
(i) Warming of our palms when we rub them.
(ii) Rubbing sticks together to produce fire.
(iii) Warming of the parts of a machine when it is operated.

If we touch the strip and standing on ground (not on any insulating base), the charges will pass through our hand because it will get the path of flow and strips will contract.

Plastics find extensive use in the health care industry. They are used in packaging of tablets, making threads used for stitching wounds, syringes, doctor's gloves and a number of medical instruments.

The advantages of using CNG and LPG as fuels are as follows :
(i) CNG and LPG are clean fuels.
(ii) They do not produce pollution.
(iii) They are easily available.
(iv) They can be used directly for burning.
(v) They are easy to transport.
(vi) Their cost is low.

Microorganisms are divided into four major groups which are as follows:
(i) Bacteria These are single-celled organisms which are harmful, as they cause disease and some of them may be useful as in. vaccines.
(ii) Fungi These are non-green plants which consume their food from the dead organic matter.
(iii) Protozoa These are unicellular animals which causes diseases like malaria and dysentery.
(iv) Algae These are photoautotrophic organisms, that may be unicellular or multicellular. They play important role in medicines, agriculture, industry and as food. Some microbiologists also classify viruses as microorganisms, but other consider these as non-living. They are those microbes which reproduce only inside the cells of host organisms. They cause diseases like cold, polio, AIDS, etc.

An earthquake is a sudden shaking of earth's plates due to collision. When earthquake occurs, then we suffer a huge loss of life and property.

Coal-tar is used as starting material for manufacturing various substances used in everyday life and in industry, like synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials etc.

By introducing vaccine in body, the body fights and kills the bacteria by producing suitable antibodies. The antibodies remain in the body and the child is protected from the disease causing microbes.

Nylon thread is stronger than a steel wire.

The bulb does not glow because the current through it is too weak.

Since, wet hand acts as good conductor. So, we feel electric shock when we touch electrical appliance with wet hands.

Thunderstorm, lightning and cyclones are the natural phenomena that can be predicted.

In India, coal is found mainly in Bihar, West Bengal, Orissa and Madhya Pradesh.

The raw materials used in making nylon are coal, water and air.

Spherical bacteria are called as cocci.

Across:
1. Lubricants
2. Static
3. Interlocking
Down:
4. Ball bearing
5. Drag
6. Rolling

1. Seismograph,
2. Richter,
3. Earthquake,
4. Conduction.

Plastic is non-biodegradable and causes environmental pollution as it takes several years to decompose. It is not environment friendly. When the plastic waste materials are burnt, they burn very slow. They do not get completely burnt. In the burning process, they release lots of poisonous fumes (gases) into the atmosphere causing air pollution. The animals eat up the polythene bags and wrappers of food along with the leftover food thrown on garbage dumps.
The methods to limit its consumption are:
Reducing its use; reusing it for some other purposes and recycling. It may reduce environmental pollution also.

We take CuS04 solution and dip a pure copper plate as cathode (-ve) and impure copper plate as anode (+ve). Due to voltage of battery, the impurities from the impure sample slowly deposit at the bottom and the copper plate becomes purified .

Because needle tip has very less area of cross-section in comparison to that of our finger and we know that pressure exerted by a force is inversely proportional to the area where it has been applied, so pressure exerted will be more by the needle tip than the finger.

It is not safer to use wired telephone during lightning because at that time lightning can enter the wire of telephone, if open somewhere, that is if there is any cut in the wire. On the other hand, there cannot be any possibility of this type in wireless telephone.

Fossil fuels will last only for a few hundred years because they are exhaustible natural resources. If consumed at a rate faster than the rate at which these are formed in nature, they will get exhausted very soon.
Once the present stock of these gets exhausted, no new supplies of these fossil fuels will be available to us in the near future because it required millions of years for the conversion of dead organisms into these fuels.

(a) Cholera By maintaining personal hygiene and good sanitation practices.
(b) Typhoid Eating properly cooked food, drinking boiled water and by getting vaccinated against the disease.
(c) Hepatitis-A Drinking boiled water and getting vaccinated against the disease