Energy Forms and Sources - Class XII

Hydroelectric energy, also referred to as hydroelectricity or hydropower, is the use of moving water to produce electricity. This power is generated by converting the kinetic energy of flowing water into mechanical and then electrical energy. This process involves the use of turbines, which consist of a set of blades. The moving water flows over the blades, causing them to turn. The blades are connected to a rotating drive shaft. The mechanical energy of the drive shaft is transferred to a generator through a gearbox. The generator uses the mechanical energy of the drive shaft to move an electric conductor (typically coils of copper wire) through a magnetic field, which causes electrons to flow through the conductor, generating electricity. The electricity is then fed into the electrical grid to be used in homes, businesses, and by industry.
Hence, the statement is true.

Answer is A.

It is because they are actually fossils. They are made of dead and decay matter buried under the earth for many years. The dead and decaying matter under great amount of pressure and temperatures turn into fossils and they both are used as fuels so it is called fossil fuels.
The fossil fuels we use today are actually formed from plants and animals that existed hundreds of millions of years ago. The reason there is a lot of concern surrounding the expenditure of these resources is because most of what we use today from fossil fuels, such as oil and coal are being depleted much faster than they can be formed, so there is a limited amount available.
Hence, the statement is true.

Fossil fuels are formed when plants and marine species are buried below ground and are subjected to immense pressure and temperature for thousands of years. Examples include coal, petroleum and natural gas.

All fossil fuels are non- renewable source of energy. Since coal is a fossil fuel so, it is a non renewable resource.

A solar cell gathers sunlight. It is the light energy which is converted into electrical energy.

Solar panel refers either to a photovoltaic module, a solar hot water panel, or to a set of solar photovoltaic (PV) modules electrically connected and mounted on a supporting structure. A PV module is a packaged, connected assembly of solar cells. Solar panels can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications.

In the box type solar cooker, the heat from the sunlight is used to cook the food.

Solar water heater works on solar radiation falling on it. It requires solar light for generating enough heat to heat water. During cloudy days, Sun is obstructed by clouds, and the light incident of the solar panels will be inefficient to make the heater work.

A solar cell (photovoltaic cell) is a device that converts light energy (photons from the sun) directly into electrical energy through the photovoltaic effect.

A photovoltaic cell is specifically designed to convert solar (light) energy into electrical energy.

Solar cells convert solar energy (light) into electrical energy.

Photovoltaic cells use the photovoltaic effect to convert solar energy (light) into electricity.

A solar cell converts light energy into electrical energy. Since this option is not listed, 'none of these' is the correct choice.

Solar heating device first converts heat energy of Sun to heat up a substance, which is then converted to electrical energy.

Solar panel uses multiple solar cells to increase electricity produced by the system.

Solar panel uses multiple cells to add up electricity output from the system.

Solar cell converts light energy of sun into electrical energy.

Solar cells have access only to the solar energy and chemical energy (battery embedded in satellite system). However, chemical energy is limited. Hence, solar energy is the standard source of energy used in satellites.

Group of solar cells is called solar panel.

Solar cell produces pure electricity with no waste products and is environment friendly. 

When light energy is incident on Si, it is converted to electricity by the principle of photovoltaic effect. GaAs, InP are other materials with similar property. 

The cost of solar cells is reducing exponentially.

Solar energy production on a large scale is difficult on a large scale because:

Black surfaces are good absorbers and good radiators of heat and hence painting the surface black traps more heat and improves the efficiency of solar cooker.

The reflector on the top of the solar cooker is used to focus the solar energy over the glass surface. The mirror reflects the heat energy in a confined area and increases the net input energy to the solar cooker.

Solar cells are fitted on a scientific calculator.

Production of solar cells is increasing exponentially every year.

Solar cell works on the principle of photovoltaic effect according to which free electrons are produced when light of certain wavelength is incident on semiconductors.

Rotation of Earth about the Sun causes the position of Sun to change during the day. Hence, the mirror on the top of the solar cooker needs adjusting during the day to focus the rays in a small area.

Solar cooker is a device used to collect the solar energy in the form of heat.

To improve the efficiency of a solar cooker, the following steps need to be done:

Solar cooker is a device that uses energy from the Sun directly to cook food or warm fluids.

Concave or plain mirror are used on the top cover of the cooker. Light get reflected from these mirrors, these mirrors concentrates the light onto a point or a region where the food is kept to be cooked.

Concave or plain mirror is used in the solar cooker in order to concentrate the sunlight at one spot.

Interior of the solar cooker is painted black inorder to absorb maximum of the Sun's light falling on the device.

Solar panel is a very useful device. Some of its major advantages are:

Solar devices are dependent on the sunlight for the generation of electricity. For the solar device to work efficiently, sunlight with good intensity should be available. Sunlight is weak during cloudy and rainy days. 

Solar panels are used to convert light (from solar energy) into electricity.

Solar panels can be used in calculators and battery operated toys, in satellites and Mars probes to provide them with energy to function in outer space by using the Sun's rays, can be used in traffic signals etc.

Solar panels are dependent on the sunlight for the generation of electricity. For the solar panels to work efficiently, sunlight with good intensity should be available to fall on the panels. Sunlight is weak during cloudy and rainy days. Hence, solar panels cannot produce energy throughout the year.

Solar constant is defined as the mean amount of the solar energy received by the Earth's atmosphere, per unit of the area, during the time when the Earth is at the mean distance from the Sun. Solar constant equals to 1388 watts per square meter.

Solar cells are devices that converts Sun's radiation energy into electricity. Solar cells contains a semiconductor. Silicon is a good semiconductor that can be used for the production of solar cells.

A solar water heater cannot be used to get hot water on a cloudy day as there is no Sun which is necessary for the working of solar water heater.

Solar cookers use thermal energy to cook food. While heat can affect some vitamins, the process does not inherently destroy all vitamins, and the statement is generally considered false in this context.

In parabolic solar cooker, the container of cooking is placed at the focal point of mirror so that all rays that are falling on solar cooker can converge to one point and produce large amount of heat energy.

The device used in traffic signal lights is Solar traffic light. are signalling devices powered by solar panels positioned at road intersections, pedestrian crossings and other locations to control the flows of traffic. 

Water always flow due to pressure difference generated by heat in solar cooker.

1. Clean the glass cover regularly .
   2.Prevent nay shade of the collector.
   3. Be economical with the use of water.
   4.Run the hot water slowly ; this will avoid the mixing of hot and cold water in the storage tank.
   5.Set the thermostat of the electrical backup as low as is comfortable.
   
   
   So this what you have to do to maintain your solar cooker as you can see it will require very less cost for maintenance.

The box contains copper tubes  bent in the form of a coil (zig-zag shape). This is done to increase the surface area  for absorbing heat.

Solar cells are made of semiconductor materials like silicon, gallium, or germanium. Platinum is a metal and is not a semiconductor, so it cannot be used to make a solar cell.

A solar cell is specifically designed to convert light energy into electrical energy.

Silver is the metal which is used for connecting wires that connect solar cells in a solar panel, due to its large conductivity.

A box-type solar cooker requires a material with good thermal conductivity (like copper) and an inner surface painted black to maximize the absorption of solar radiation.

Solar cell use light energy from photons (basic unit of light energy) and convert it to electricity using semiconductor physics.

A pressure cooker increases the pressure inside the vessel, which raises the boiling point of water. This allows the food to cook at a higher temperature, significantly reducing cooking time.

A solar cell converts light energy into electrical energy.

Photovoltaic cells, commonly known as solar cells, convert light energy directly into electricity. They utilize the photovoltaic effect to generate current when exposed to solar radiation.

The total surface area of solar cells on which solar energy is falling = area of each cell $\times$ number of cells $= 4 \times 3000 {cm}^{2} = 1.2  {m}^{2}$
The solar energy falling on 3000 cells 
${Q} _{1} = 1.2 \times 640  J = 768  J$
The energy converted into electric energy $= \displaystyle\frac{20}{100} \times 768 = 153.6  J$
The electric energy generated in one second is $153.6  J$

A spherical reflector (concave mirror) concentrates solar rays to a single focal point, significantly increasing the temperature. Proper insulation of the cooker is also essential to minimize heat loss to the surroundings, allowing the temperature to reach high levels.

No On cloudy day solar cooker did not get sufficient amount of sunlight to produce heat energy for cooking.

If we did not adjust the parabolic mirror in solar cooker according the  movement of sun then all ray of sunlight cannot converge at one point .hence  with time we will get lesser amount of heat energy.

Output of solar cell occurs at a constant voltage. Using a group of solar cells in the solar panel increases the amount of current produced. Also, as area is increased more solar energy is captured and more electrical energy is produced.

 Solar energy systems/power plants do not produce air pollution, water poullution, or greenhouse gases. ... However, some toxic materials and chemicals are used to make the photovoltaic (PV) cells that convert sunlight into electricity.

Among all colour black is the best absorber for heat  so outer surface of copper tube is coloured with black.

The most common way of capturing the energy from geothermal sources is to tap into naturally occurring 'hydrothermal convection' systems, where cooler water seeps into Earth's crust, is heated up, and then rises to the surface. Once this heated water is forced to the surface, it is a relatively simple matter to capture that steam and use it to drive electric generators. Geothermal power plants drill their own holes into the rock to more effectively capture the steam.
Hence, the statement is true.

Potential of single smaller Hg drop of water =$\dfrac{Kq}{r}$=V-----(1)

Since potential energy defined only for conservative force. It will increase for conservative force.

We know that potential energy is the energy possesd by the virtue of its position.
So, $F = mgh $
Where, $ m = $ mass
So, From above equation we can deduce that potential energy depends on the mass of the substance.

Potential energy of a body is defined as energy possessed by a body by  virtue of its position at a height.
$ P.E = mgh$

Nuclear fission

Blast yard of little bys is equivalent to 15 kilotons(15000 tons)  of TNT. 

Fission-fusion-fission 

E

Plutonium 239

C

A, B and C

Uncontrolled fusion reaction 

lnfrared radiation, often abbreviated as IR, the large band of infrared wavelengths extends from the far-red portion of the visible light spectrum (around 700 - 780 nanometers) to about one millimeter in wavelength. This type of radiation is associated with the thermal region where visible light is not necessarily detectable or even present. As high temperature is developed at the moment of atomic explosion the wavelength of the light coming from that region lie in the infrared region.

An atomic bomb consists of two pieces of $ _{ 92 }{ U }^{ 235 }$ (or $ _{ 94 }{ Pu }^{ 219 }$) (plutonium) each smaller than the critical size and a source of neutrons

The reactor with conversion ratio greater than 1 is called a breeder reactor. This is the reactor that produces more fuel than it consumes. In atomic reactor Neutron ratio is greater than 1.