PHYSICS [3 Mark Question Answer]

Nuclear waste: Nuclear waste is the material that nuclear fuel becomes after it is used. in a reactor.
Hazards of nuclear waste:
(i) Nuclear waste can cause environmental contamination which can affect the health of millions of people.
(ii) Nuclear waste is the source of radiations which can lead to the following disorders:
(a) Radiations can cause genetic disorders.
(b) These can cause leukemia.
(c) These can destroy the immunity and hence may lead to death.
(d) Long exposure to radiations can cause cancer, blindness etc.

Advantages of Hydel Power:
1. It does not produce any environmental pollution.
2. It is renewable source of energy.
3. Dam help us in irrigation and they control floods.
Limitations of Hydel Power:
1. The flowing water is not available every where
2. The ecological balance in the downstream areas of rivers gets disturbed.

Windmill : It is a machine which converts kinetic energy of wind into electrical energy. A windmill consists of two or three blades like an electric fan which rotates about an axle mounted on a pole.
The shaft of the windmill is connected to the shaft of armature of a generator. When the fast moving wind rotates the blades of windmill, its shaft rotates the armature inside the generator. The rotating armature produces electric current. Thus, the kinetic energy of wind is converted into electric energy.

(a) Kinetic energy is possessed by wind.
(b) Advantages of wind energy:
1. It does not cause any kind of pollution.
2. It is a renewable source.
Limitations of wind energy:
1. The wind farms can be establishes only at places when wind blows around the year steadily.
2. A large area of land is needed to establish a wind farm.

(a) Semiconductors: Those materials whose conductivity is less than conductors but more than insulators are known as semiconductors.
Semiconductors are neither good conductors nor insulators of electricity. Germanium (Ge) and Silicon (Si) are the two semiconductors.
(b) Doping: The process of adding impurities to semi conductors is called doping. Materials used for doping are Boron and phosphorous.
Advantages of doping the semiconductors: Semi conductors are doped to increase the conductivity of the semiconductor.

Renewable sources:
1. These are the sources from which energy can be obtained continuously over a long period of time.
2. They are non-conventional sources.
3. These are the natural sources which will never get exhausted.
4. These sources can be regenerated.
5. Examples: Solar energy, wind energy, hydro-energy, geo-thermal energy and nuclear energy.
Non-renewable sources:
1. These are the sources from which energy can not be continuously obtained over a long period of time.
2. They are conventional sources.
3. These are natural sources which ould soon depletes.
4. These sources cannot be regenerated.
5. Examples: Coal, petroleum and natural gas.