Question Paper: may 2018 EVS solved paper of Mumbai University part 2

3A. How is electricity generated by using wind energy.

Wind power converts the kinetic energy in wind to generate electricity or mechanical power. This is done by using a large wind turbine usually consisting of propellers; the turbine can be connected to a generator to generate electricity, or the wind used as mechanical power to perform tasks such as pumping water or grinding grain. As the wind passes the turbines it moves the blades, which spins the shaft. There are currently two different kinds of wind turbines in use, the Horizontal Axis Wind Turbines (HAWT) or the Vertical Axis Wind Turbines (VAWT). HAWT are the most common wind turbines, displaying the propeller or ‘fan-style’ blades, and VAWT are usually in an ‘egg-beater’ style. Converting Wind to Mechanical Energy Wind is converted by the blades of wind turbines. The blades of the wind turbines are designed in two different ways, the drag type and lift type.

• Drag type: this blade design uses the force of the wind to push the blades around. These blades have a higher torque than lift designs but with a slower rotating speed. The drag type blades were the first designs used to harness wind energy for activities such as grinding and sawing. As the rotating speed of the blades are much slower than lift type this design is usually never used for generating large scale energy.

• Lift type: most modern HAWT use this design. Both sides of the blade has air blown across it resulting in the air taking longer to travel across the edges. In this way lower air pressure is created on the leading edge of the blade, and higher air pressure created on the tail edge. Because of this pressure difference the blade is pushed and pulled around, creating a higher rotational speed that is needed for generating electricity.

Creating Electricity from Wind To create electricity from wind the shaft of the turbine must be connected to a generator. The generator uses the turning motion of the shaft to rotate a rotor which has oppositely charge magnets and is surrounded by copper wire loops. Electromagnetic induction is created by the rotor spinning around the inside of the core, generating electricity.

Distribution of Electricity The electricity generated by harnessing the wind’s mechanical energy must go through a transformer in order increase its voltage and make it successfully transfer across long distances. Power stations and fuse boxes receive the current and then transform it to a lower voltage that can be safely used by business and homes.

3B state and explain principle, construction and working of flat plate collector used for the solar energy

Ans:- Principle and working of Flat Plate Collector

A Flat Plate Collector is a heat exchanger that converts the radiant solar energy from the sun into heat energy using the well known greenhouse effect. It collects, or captures, solar energy and uses that energy to heat water. If a metal sheet is exposed to solar radiation, the temperature will rise until the rate at which energy is received is equal to the rate at which heat is lost from the plate; this temperature is termed as the ‘equilibrium’ temperature. If the back of the plate is protected by a heat insulting material, and the exposed surface of the plate is painted black and is coved by one or two glass sheets, then the equilibrium temperature will be much higher than that for the simple exposed sheet.


(i) Glazing, which may be one or more sheets of glass or other diathermanous (radiation transmitting) material

(ii) Tubes, fins or passages for conducting or directing the heat transfer fluid from the inlet to the outlet.

(iii) Absorber plate which may be flat, corrugated or grooved with tubes, fins or passages attached to it.

(iv) Header or manifolds, to admit and discharge the fluid.

(v) Insulation which minimizes heat loss from the back and sides of the collector.

(vi) Container or casing which surrounds the various components and protects them from dust, moisture etc.

3C what are the limitations of conventional sources of energy Answer:-

  1. Time consuming to extract. Mining coal, searching for oil, and building drills and pipes to extract and transport natural gas, are all very time consuming processes. This energy takes a lot of effort to get hold of

  2. Contribution to climate change. Burning coal, oil and natural gas releases large amounts of carbon dioxide and carbon monoxide which are major contributors to global warming. These chemicals destroy the ozone layer, make the oceans acidic and saturated with carbon, and make the air more difficult for animals to breathe and plants to flourish in. By creating a ‘mantle’ of carbon rich air in the atmosphere, moreover, these chemicals trap the sun’s rays and make the atmosphere around the earth much warmer: this is the so-called greenhouse effect. It is called the greenhouse effect because it makes the atmosphere like a giant warm greenhouse.

  3. Contribution to acid rain. Burning fossil fuels releases oxides (including sulfur oxide) which cause rain to become acidic. This is very harmful to wildlife and also erodes buildings.

  4. Dangerous for humans. Non-renewable energy sources like fossil fuels can emit carbon monoxide. This is dangerous to humans and can cause respiratory problems and death if inhaled. It is especially dangerous because it is colorless and odorless and thus not detectable by the human eye or sense of smell. We might ask ourselves whether using non-renewable fuels is worth the risk when there are many less dangerous renewable energy sources out there.

  5. Not viable for future generations. Because they are, by definition, non-renewable, non-renewable energy sources will eventually run out. That means that humans will not be able to base our lives on them forever. In fact, our reserves of many non-renewables may run out by the end of this century. Using non-renewable energy sources without taking steps to make our infrastructure, homes and factories ready to use renewable sources of energy could be said to be very selfish. Moreover, using up all the non-renewable sources of energy now, without leaving any for future generations, can also be said to be a selfish act.

  6. Dirty. Many non-renewable sources of energy are quite dirty, leaving soot and dirt on furnishings in the home. When used in factories, they release soot and other dirty substances into the air which can coat buildings and pavements, and make cities feel dirty and grimy. One reason for the unsightliness of modern cities – which some people complain about – and the smog that can make them seem dark and overcast, is the overuse of dirty, non-renewable sources of energy.

4A what are green buildings? What are the advantages of green structure.

Ans:- A ‘green’ building is a building that, in its design, construction or operation, reduces or eliminates negative impacts, and can create positive impacts, on our climate and natural environment. Green buildings preserve precious natural resources and improve our quality of life. when going green that we are able to reduce their carbon footprint and actually lend a helping hand to the environment. Green buildings are designed in such a way to reduce overall impact on environment and human health by:

i. Reducing trash, pollution and degradation of environment.

ii. Efficiently using energy, water and other resources.

iii. Protecting occupant health and improving productivity.

Environmental Benefits: • Reduce wastage of water • Conserve natural resources • Improve air and water quality • Protect biodiversity and ecosystems

Economic Benefits: • Reduce operating costs • Improve occupant productivity • Create market for green product and services

Social Benefits:

• Improve quality of life • Minimize strain on local infrastructure • Improve occupant health and comfort

4B discuss various indoor air pollutants

(1) Pollutant: carbon monoxide (CO) Carbon monoxide is an odorless, invisible gas. It’s produced by the incomplete combustion of fossil fuels.

Risks: Carbon monoxide stops your body from using the oxygen it needs to work normally. You may experience tiredness, headaches, dizziness, nausea, confusion, and a fast heart rate. If the concentration of carbon monoxide is high enough, you could die.

What you can do: The Environmental Assistance and Protection Department of Forsyth County, North Carolina recommends having your heating systems checked by a professional yearly. Make sure that combustion appliances, such as heaters, have been installed correctly. Do not use combustion appliances without vents inside and never use a gas stove to heat your house.

(2) Pollutant: radon Radon is an odorless, colorless gas that is found everywhere in low levels. It is made naturally as the uranium in the Earth breaks down. Risks:

Being exposed to elevated levels of radon increases your risk of getting lung cancer. What you can do:

You should screen your home for elevated radon levels with a kit or have it tested by a qualified professional. Radon screening kits are easy to use and can be purchased online with your credit card. For example, the company Radon Environmental, Inc. offers a radon homeowner’s testing kit for $35 via radon-environmental.com. You can pay using a Visa, Mastercard, or American Express card. If your home does have elevated levels of radon, you must hire a qualified professional to remove it.

(3) Pollutant: nitrogen dioxide (NO2) Nitrogen dioxide (NO2) is a common oxide of nitrogen. It is a toxic and corrosive gas. Please note that nitrogen dioxide (NO2) is different from nitrous oxide (N2O), an oxide of nitrogen that is medically useful when administered by trained professionals, such as dentists.

Risks: Nitrogen dioxide (NO2) irritates the throat, eyes, nose, and respiratory tract. Exposure to very high doses of NO2, such as at the site of a building fire, can lead to pulmonary edema (potentially fatal liquid build-up in the lungs) or lung injury. Moderate exposure can lead to acute or chronic bronchitis. Low-level exposure can impair lung function for people who are already at risk, such as asthmatics, people with chronic obstructive lung disease, and children.

What you can do: According to the U.S. Environmental Protection Agency, it’s important to ensure that combustion appliances, such as heaters, are installed correctly, used as directed, and kept in good condition. Make sure the air from these appliances can flow outdoors. Do not idle your car in the garage.

(4) Pollutant: secondhand smoke Secondhand smoke, also called environmental tobacco smoke, comes from incompletely burned tobacco products. According to the Environmental Assistance and Protection Department of Forsyth County, secondhand smoke contains over 4,700 chemical ingredients.

Risks: In the short term, exposure to secondhand smoke can cause eye, nose, and throat irritation. In the long-long, it can cause many of the same health problems as smoking, like wheezing, pneumonia, bronchitis, and lung cancer. Asthma attacks may be triggered by secondhand smoke exposure.

What you can do: Do not smoke cigarettes, cigars, or pipe tobacco inside your home and do not allow others to do so.

(5) Pollutant: lead particles Lead is a natural, soft metal that is very toxic if consumed. Lead was widely used in house paint until it was banned in 1978. Lead particles and dust can become airborne, leading to dangerous indoor air pollution.

Risks: Exposure to lead can damage the brain, nervous system, kidneys, and red blood cells. If children are exposed, they may develop short attention spans, behavioral problems, lower IQ levels, and delayed growth.

What you can do: If you live in a home painted before 1978, the Environmental Assistance and Protection Department of Forsyth County advises keeping play areas clean, mopping floors frequently, and using damp cloths to wipe window ledges and flat areas often. Keep kids away from chipped or peeled paint, clean their toys often, and make sure they wash their hands before eating.

(6) Pollutant: asbestos Asbestos is the name used for a group of minerals found naturally all over the world. The U.S. Environmental Protection Agency declared asbestos unsafe in 1971, listing it as a hazardous air pollutant. Although asbestos is not hazardous when intact, disturbing asbestos fibers causes them to become airborne, where they could potentially enter the lungs.

Risks: In the long-term, exposure to asbestos can lead to various lung disorders, including lung cancer and asbestosis. Asbestosis is an inflammatory condition of the lungs that causes coughing, trouble breathing, and permanent lung damage. Those affected by asbestos should consult asbestos exposure lawyers.

What you can do: If products in your home contain asbestos, but are in good condition, the Environmental Assistance and Protection Department of Forsyth County recommends just keeping them in good condition. Otherwise, have them removed by a trained professional.

(7) Pollutant: mold Molds are types of fungi that grow indoors and outdoors. Some types of mold are harmless, while others are dangerous.

Risks: Mold can trigger an allergic reaction in some people. Symptoms can include nasal stuffiness, eye or throat irritation, swelling, coughing or wheezing, headaches, or skin irritation. Severe reactions can lead to fever and trouble breathing. Mold can also trigger asthma attacks.

What you can do: According to the Environmental Assistance and Protection Department of Forsyth County, the key to fighting mold is keeping moisture and humidity levels in check. Fix leaks and clean up spills ASAP. Make sure appliances that create moisture are vented. Keep the bathroom fan on or the window open when taking a shower.

4.C what is the role of disaster management?

National Disaster Management Authority, abbreviated as NDMA is an agency of the Ministry of Home Affairs whose primary purpose is to coordinate response to natural or man-made disasters and for capacity-building in disaster resiliency and crisis response. NDMA is operationally organized into the following divisions:

• Policy & Planning

• Mitigation

• Operations & Communications

• Administration

• Capacity Building

Role of disaster management

• Lay down policies on disaster management;

• Approve the National Plan;

• Approve plans prepared by the Ministries or Departments of the Government of India in accordance with the National Plan;

• Lay down guidelines to be followed by the State Authorities in drawing up the State Plan;

• Lay down guidelines to be followed by the different Ministries or Departments of the Government of India for the Purpose of integrating the measures for prevention of disaster or the mitigation of its effects in their development plans and projects;

• Coordinate the enforcement and implementation of the policy and plans for disaster management;

• Recommend provision of funds for the purpose of mitigation;

• Provide such support to other countries affected by major disasters as may be determined by the Central Government;

• Take such other measures for the prevention of disaster, or the mitigation, or preparedness and capacity building for dealing with threatening disaster situations or disasters as it may consider necessary;

• Lay down broad policies and guidelines for the functioning of the National Institute of Disaster Management.


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