solar cell experiment viva questions with answers pdf
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Solar cell experiment viva questions with answers pdf
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Solar Cells - Test Questions

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Question 71
Question 72
Question 73
Question 74
Question 75
Question 76
Question 77
Question 78
Question 79
Question 80

Question 71Back to Top
Question: List the uses of solar cells.

Answer: A Solar cells or solar cell panels are used in:
1) Artificial satellites and in space probes like Mars orbiters
2) Wireless transmission systems or TV relay stations in remote locations
3) Traffic signals, calculators and in toys

Question 72Back to Top
Question: Explain the working of tidal energy power plant with a neat diagram.

Answer: During high tide, when the level of water in the sea is high, sea-water flows into the reservoir of the barrage and turns the turbines. The turbines then turn the generator shaft to produce electricity.

image

During low tide, the sea-water stored in the barrage reservoir is allowed to flow out into the sea. This flowing water also turns the turbines and generates electricity. Thus, as the sea-water flows in and out of the tidal barrage during high and low tides, the turbines rotate continuously to generate electricity.


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The energy conversion involved in a tidal power plant is given below:

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Question 73Back to Top
Question: Write a short note on ocean thermal energy.

Answer: The water at the surface of an ocean gets heated by the heat of the sun and attains a higher temperature than the colder water at deeper levels in the ocean. So, there is always a temperature difference between the water "at the surface of ocean" and "at deeper levels." At many places in the ocean, this difference in temperatures of water is up to 20oC. The energy available due to the difference in the temperature of water at the surface of the ocean and at deeper levels is called ocean thermal energy (OTE). The ocean thermal energy can be converted into "usable form" of energy like electricity. This can be done as follows:

The devices used to harness ocean thermal energy are called Ocean Thermal Energy Conversion power plants (or OTEC power plants). In one type of OTEC power plants, the warm surface water of ocean is used to boil a liquid like ammonia or a chlorofluorocarbon (CFC). The high pressure vapours of the liquid (formed by boiling) are then used to turn the turbine of a generator and produce electricity. The colder water from the deeper ocean is pumped up to cool the used up vapours and convert them again into a liquid. This process is repeated again and again.

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Advantages
1) A greater advantage of the ocean thermal energy is that it can be used continuously for 24 hours throughout the year.

2) Ocean thermal energy is a renewable source of energy and its use does not cause any pollution. Sea-wave energy and ocean thermal energy are the two forms in which solar energy manifests itself in oceans.

Limitation
1) The installation and maintenance of an OTEC power plant is very high and efficient commercial exploitation is difficult.

Question 74Back to Top
Question: List the hazards of nuclear power generation.

Answer: 1) In case of accidents or explosion, the radioactive materials can contaminate vast areas of land, crops, water, people etc

2) The number of safety measures that has to be considered before setting up a plant makes the construction of the plant expensive

3) The disposal of radioactive wastes in the fission process is a major problem. Expensive long-term storage areas have to be built

4) They also pose security problems, as the fuel and the by-products can be used to build nuclear weapons

Question 75Back to Top
Question: What steps would you suggest to consume energy effectively?

Answer: 1) Coal should be burnt in specially designed Chulhas or Angittees to get maximum heat energy

2) We should not burn cow-dung cakes directly but should use in the production of biogas which is more efficient and cleaner

3) LPG must be used properly and checked for any leakage

4) Electrical appliances must be switched off when not required

5) Engines of vehicles must be checked regularly to make sure that they consume the right quantity of fuel

Question 76Back to Top
Question: What is a fuel? Give any four characteristics of a good fuel.

Answer: Any substance which is available easily and burns in air at moderate rate, producing large amount of heat energy, without leaving behind any undesirable residues is called a fuel. Characteristics:
1) Should be cheap and easily available
2) Easy to store
3) Should not pose any hazards during transportation
4) High calorific value

Question 77Back to Top
Question: Explain the construction and working of a hydro-electric power plant with a neat schematic diagram.

Answer: Principle The water flowing in a river is collected by constructing a high rise dam. This stored water is then allowed to fall from the top of the reservoir on to a water turbine located at the bottom of the dam. The fast moving water rotates the blades of the water turbine, which in turn rotates the armature of the generator and produces electricity.

Construction and Working

image

Water flowing in high altitude rivers is stored in a man-made reservoir as shown in the figure. The kinetic energy of the flowing water is transformed into potential energy as the water level rises. This water is carried through pipes to the turbine situated at the bottom of the dam. The water turbine has cup-shaped discs around its circumference. A jet of moving water rotates the water turbine rapidly which in turn rotates the shaft which is attached to its centre. The other end of the shaft is connected to the coil of an electric generator. The generator coil rotates and produces electricity.

Question 78Back to Top
Question: Briefly explain the construction and working of a fixed dome type biogas plant.

Answer: Raw Materials Required
Forms of biomass listed below may be used along with water:
1) Animal dung
2) Poultry wastes
3) Plant wastes (Husk, grass, weeds etc.)
4) Human excreta
5) Industrial wastes(Saw dust, wastes from food processing industries)
6) Domestic wastes (Vegetable peels, waste food materials)

Principle
Biogas is produced as a result of anaerobic fermentation of biomass in the presence of water.

Construction
The biogas plant is a brick and cement structure having the following five sections:

1) Mixing tank present above the ground level

2) Inlet chamber: The mixing tank opens underground into a sloping inlet chamber

3) Digester: The inlet chamber opens from below into the digester which is a huge tank with a dome like ceiling. The ceiling of the digester has an outlet with a valve for the supply of biogas

4) Outlet chamber: The digester opens from below into an outlet chamber

5) Overflow tank: The outlet chamber opens from the top into a small over flow tank

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Working
1) The various forms of biomass are mixed with an equal quantity of water in the mixing tank. This forms the slurry

2) The slurry is fed into the digester through the inlet chamber. The temperature of the slurry must be maintained around 35 oC. Any drop in temperature will reduce the anaerobic activity and hence the yield of biogas

3) When the digester is partially filled with the slurry, the introduction of slurry is stopped and the plant is left unused for about two months

4) During these two months, anaerobic bacteria present in the slurry decompose or ferment the biomass in the presence of water

5) As a result of anaerobic fermentation, biogas is formed, which starts collecting in the dome of the digester

6) As more and more biogas starts collecting, the pressure exerted by the biogas forces the spent slurry into the outlet chamber

7) From the outlet chamber, the spent slurry overflows into the overflow tank

8) The spent slurry is manually removed from the overflow tank and used as manure for plants

9) The gas valve connected to a system of pipelines is opened when a supply of biogas is required

10) To obtain a continuous supply of biogas, a functioning plant can be fed continuously with the prepared slurry


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Question 79Back to Top
Question: Explain the working of two devices that use solar energy.

Answer: A solar heating device is one which allows collection of a large amount of heat from the sunlight in a given region and restricts the loss of heat to the surrounding in the form of radiation.

image

The following facts help us to design an efficient solar cooker.
1) A black body absorbs maximum heat
2) Loss of heat by convection can be restricted in a closed system
3) Radiation losses can be avoided by reflecting the rays inside the body with the help of reflecting object like a plane mirror
4) Conduction can be reduced by using poor conducting materials
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