Science, Unit 7, Unit 8

 Unit - 7

Energy

* Answer the following questions:

(a) Give the definition of power.

Power can be defined as the ability or capacity to do or accomplish something, to exert control or influence over others, or to produce an effect or result.

(b) What is the source of power?

The source of power can vary depending on the context. In general, power can originate from various sources such as physical strength, knowledge, wealth, social status, authority, charisma, or access to resources.

(c) Name any four sources of power.

Four sources of power:

1. Physical power: Refers to the strength, stamina, or physical capabilities of an individual.
2. Knowledge power: Relates to the possession of specialized knowledge, skills, or expertise in a particular field.
3. Positional power: Arises from one's official or formal position within an organization or society, granting certain authority and decision-making abilities.
4. Financial power: Derives from wealth, financial resources, or control over economic assets.

(d) Name any four forms of power.

Four forms of power:

1. Coercive power: Involves the use of threats, punishment, or negative consequences to gain compliance or control over others.
2. Reward power: Involves the ability to provide incentives, rewards, or positive benefits to influence or motivate others.
3. Legitimate power: Stems from the recognition of one's authority, position, or status within a social or organizational hierarchy.
4. Referent power: Arises from admiration, respect, or personal connection, where others are influenced by the charisma, personality, or characteristics of an individual.

(e) Write any five meanings of Shakti.

Meanings of Shakti:

1. Shakti is a Sanskrit term that translates to "power" or "energy" and is often associated with the feminine aspect of divine energy in Hinduism.
2. Shakti can refer to the primordial cosmic energy that is believed to be the source of creation, preservation, and destruction in Hindu philosophy.
3. Shakti can also signify the divine feminine energy or goddesses, such as Durga, Kali, or Lakshmi, who embody different aspects of power, strength, and creativity.
4. Shakti can symbolize the inherent power or potential within an individual, representing their inner strength, vitality, or capability.
5. In some traditions, Shakti is also used to denote the Kundalini energy, which is believed to be a powerful spiritual force that can be awakened through various practices like meditation and yoga, leading to spiritual transformation and enlightenment.

* Give reasons:

(a) Sun is considered as the main source of energy.

The sun is considered as the main source of energy for several reasons:

1. Solar radiation: The sun emits vast amounts of electromagnetic radiation, including visible light and heat. This radiation reaches the Earth and provides energy for various processes.
2. Photosynthesis: Sunlight is essential for the process of photosynthesis in plants. Plants convert solar energy into chemical energy, which is stored in the form of glucose and used as fuel for growth and metabolism. This process forms the basis of the food chain, as other organisms depend on plants directly or indirectly for their energy.
3. Fossil fuels: Fossil fuels like coal, oil, and natural gas are formed from the remains of ancient plants and organisms that relied on solar energy during their lifetime. These fossil fuels store solar energy from millions of years ago and are extracted and used as sources of energy today.

(b) We feel weak when we do not eat.

We feel weak when we do not eat due to several reasons:

1. Energy deficit: Food provides us with essential nutrients, including carbohydrates, proteins, and fats, which are metabolized to produce energy in our bodies. When we don't eat, the body doesn't receive an adequate supply of energy, leading to an energy deficit. This energy deficit can make us feel weak, fatigued, and low in stamina.
2. Blood sugar levels: Carbohydrates from food are broken down into glucose, which is the primary source of energy for our cells. When we don't eat, our blood sugar levels drop, which can result in low energy levels, dizziness, and weakness.
3. Nutrient deficiencies: A balanced diet provides essential vitamins, minerals, and micronutrients that are crucial for the proper functioning of our body systems. When we don't eat, we may not get an adequate supply of these nutrients, leading to deficiencies. Certain nutrient deficiencies can cause weakness, fatigue, and impaired physical and mental performance.

Overall, food is not only a source of energy but also provides the necessary building blocks for our body's functioning. When we don't eat, our body lacks the fuel and nutrients it needs, resulting in weakness and other negative effects.

7.5 Conductor and Insulator Objects

* Give reasons:

  (a) In our country, hydropower is considered as the main source of electricity.

In our country, hydropower is considered as the main source of electricity due to several reasons:

1. Abundant water resources: Our country may have significant water resources, such as rivers, lakes, and reservoirs. Hydropower plants utilize the kinetic energy of flowing or falling water to generate electricity. If there is an ample supply of water, hydropower can be a reliable and continuous source of electricity.
2. Renewable and clean energy: Hydropower is a renewable energy source as it relies on the water cycle, which is naturally replenished through rainfall and snowmelt. It does not deplete natural resources and does not produce greenhouse gas emissions or air pollutants during electricity generation, making it an environmentally friendly option.
3. Cost-effective and long-term viability: Once a hydropower plant is constructed, the operational costs are relatively low compared to other conventional power sources. The equipment used for hydropower generation has a long lifespan, making it a sustainable and economically viable option for electricity production.
4. Flexibility and grid stability: Hydropower plants can quickly respond to fluctuations in electricity demand. They can be ramped up or down as needed, providing flexibility to the power grid and aiding in maintaining grid stability. Hydropower plants can also act as energy storage systems by utilizing excess electricity during off-peak hours to pump water into higher reservoirs for later use during high-demand periods.

  (b) Electricity is an important source of power.

Electricity is an important source of power due to several reasons:

1. Versatility: Electricity is a versatile form of energy that can be easily converted into various forms, such as heat, light, and mechanical energy. This versatility enables its use in a wide range of applications, including residential, commercial, industrial, and transportation sectors.
2. Convenience and reliability: Electricity is readily available at the flip of a switch, making it highly convenient for powering appliances, electronic devices, and lighting. It provides a reliable and consistent source of power when compared to other energy sources that may have limitations or depend on external factors like weather conditions.
3. Economic growth and development: Access to reliable electricity is crucial for economic growth and development. It enables the establishment and operation of industries, businesses, and infrastructure projects. Electricity powers machinery, supports communication networks, and facilitates technological advancements, which are essential for economic productivity and progress.
4. Improved quality of life: Electricity plays a vital role in enhancing the quality of life for individuals and communities. It powers essential services such as healthcare facilities, schools, and public utilities. It enables access to modern conveniences, such as electric lighting, refrigeration, heating, and cooling, improving living conditions and overall comfort.

* Answer the following questions:

  (a) Name any four devices that run on electricity.

Four devices that run on electricity:

1. Television
2. Refrigerator
3. Washing machine
4. Computer

  (b) What is the source of electricity?

The source of electricity can vary, but it is commonly generated from power plants that utilize different energy sources such as:

• Fossil fuels (coal, oil, natural gas)
• Nuclear energy
• Renewable sources (solar, wind, hydro, geothermal

  (c) Write any two uses of electricity.

Two uses of electricity:

1. Lighting: Electricity is used to power various types of lighting systems, including light bulbs, fluorescent lamps, and LED lights, providing illumination for homes, offices, streets, and public spaces.
2. Heating and cooling: Electricity is used to operate heating systems, air conditioners, fans, and heaters, providing thermal comfort and climate control in residential, commercial, and industrial buildings.

  (d) Write the names of any four sources of electricity.

Four sources of electricity:

1. Thermal power plants (coal, oil, natural gas)
2. Nuclear power plants
3. Solar power plants (photovoltaic or concentrated solar power)
4. Wind power plants (wind turbines)

  (e) How power is produced by dynamo?

Power is produced by a dynamo through electromagnetic induction. A dynamo consists of a rotating coil of wire called the armature, which is placed between the poles of a magnet. When the armature rotates, the magnetic field from the magnet induces an electric current in the wire due to the relative motion between the magnetic field and the wire. This current can be harnessed and used as electrical power.

  (f) How is hydroelectricity produced? Explain with pictures.

Hydroelectricity is produced through the following process:

1. Water reservoir: A large reservoir is created by constructing a dam on a river. The dam holds a large amount of water, forming a reservoir.

2. Penstock: The water from the reservoir is released through penstocks, which are pipes or channels that direct the water flow.

3. Turbines: The flowing water passes through turbines, which are large wheel-like structures. The force of the water causes the turbines to rotate.

4. Electricity generation: The rotating turbines are connected to generators. As the turbines spin, they turn the generators, which produce electricity through electromagnetic induction.

5. Transmission: The generated electricity is then transmitted through power lines to homes, businesses, and industries, where it can be used for various purposes.

7.15

* Answer the following questions: (a) Name any three examples of magnetic and non-magnetic objects.

Three examples of magnetic objects:

1. Magnet
2. Iron nail
3. Refrigerator magnet

Three examples of non-magnetic objects:

1. Plastic bottle
2. Wood
3. Glass

(b) What objects are called magnetic objects?

Magnetic objects are objects that are attracted to magnets or can be magnetized themselves. They include materials such as iron, nickel, cobalt, and certain alloys.

(c) Give the definition of magnetic force.

Magnetic force refers to the force exerted by magnets on magnetic objects or by magnetic objects on each other. It is a non-contact force that acts at a distance and can attract or repel objects depending on their magnetic properties.

(d) Write the difference between magnetic and non-magnetic objects.

The difference between magnetic and non-magnetic objects:

• Magnetic objects are attracted to magnets or can be magnetized, whereas non-magnetic objects are not affected by magnets.
• Magnetic objects have magnetic properties and can produce a magnetic field, while non-magnetic objects do not have such properties.
• Magnetic objects can be used to create and control magnetic fields, whereas non-magnetic objects cannot.

(e) Write any four uses of magnets.

Four uses of magnets:

1. Electric motors and generators: Magnets are used in electric motors and generators to convert electrical energy into mechanical energy and vice versa.
2. Magnetic storage devices: Magnets are used in hard drives, floppy disks, and magnetic tapes to store digital information.
3. Magnetic compass: Magnets are used in compasses to determine the direction of the Earth's magnetic field, aiding in navigation.
4. Magnetic resonance imaging (MRI): Magnets are used in medical imaging devices like MRI machines to produce detailed images of internal body structures.

(f) You have two magnets, how to find their potential Put it on, write the way.

To find the potential of two magnets, you can use the method of attraction or repulsion. Here's how:

1. Attraction method: Hold one magnet in your hand and bring it close to the other magnet. If the magnets attract each other and stick together, it indicates that they have opposite poles (north and south) facing each other. This means they have high potential.

2. Repulsion method: Hold one magnet in your hand and bring it close to the other magnet. If the magnets repel each other and push away, it indicates that they have the same poles (north and north or south and south) facing each other. This means they have low potential.

By observing the behavior of the magnets when brought close to each other, you can determine their potential based on whether they attract or repel each other.

(g) Write three differences between conductors and non-conductors.

Three differences between conductors and non-conductors:

1. Conductors are materials that allow the flow of electric current through them, while non-conductors (also called insulators) restrict or prevent the flow of electric current.
2. Conductors have a high density of free electrons, which are able to move easily within the material, facilitating the flow of current. Non-conductors have tightly bound electrons and lack free electron movement.
3. Examples of conductors include metals like copper and aluminum, while non-conductors include materials like rubber, plastic, and glass. Conductors are commonly used in electrical wiring, while non-conductors are used for insulation and protection against electric shocks.

(h) A coin with Neha falls into a deep pool. The said to him There is a great need for coins. Neha did not let the coin fall into the water How can she get it out?

Neha can try the following methods to retrieve the coin from the deep pool:

1. Using a magnet: If the coin is made of a magnetic material, Neha can use a strong magnet to attract and pull the coin out of the water.
2. Using a net or scoop: Neha can use a net or scoop with a long handle to reach into the water and scoop out the coin.
3. Draining the water: If possible, Neha can try to drain the water from the pool or create a flow of water that carries the coin towards the edge, making it easier to retrieve.

(j) Write any four properties of magnets.

Four properties of magnets:

1. Attraction and repulsion: Magnets have the property of attracting objects made of magnetic materials (like iron) and repelling objects with the same magnetic pole orientation.
2. Magnetic field: Magnets create a magnetic field around them, which is the region where their magnetic influence can be felt.
3. Poles: Magnets have two distinct poles, known as the north pole and the south pole. Like poles repel each other, while opposite poles attract each other.
4. Magnetic induction: Magnets can induce magnetism in certain materials without direct contact, causing them to become temporary magnets. This property is used in electromagnets and transformers.

 Unit - 8

The Earth and Space

The Earth

d. Write the answers to the following questions:

  (a) What type of land is found in Terai region of Nepal?

The Terai region of Nepal is primarily characterized by flat, low-lying land. It is a fertile plain situated in the southern part of Nepal, adjacent to the border of India.

  (b) What is the reason for finding less plants in the mountains?

The main reasons for finding fewer plants in the mountains are:

1. Harsh climatic conditions: Mountains often experience extreme weather conditions such as low temperatures, high winds, and limited rainfall. These conditions create a challenging environment for plant growth.
2. Steep slopes and rocky terrain: The rugged topography of mountains makes it difficult for plants to establish roots and obtain sufficient nutrients and water from the soil. The steep slopes also increase the risk of soil erosion.

  (c) Write the names of the different types of surfaces of the earth that you have seen.

The different types of surfaces of the Earth that I have seen include:

1. Land surfaces: Such as plains, hills, mountains, plateaus, deserts, and valleys.
2. Water surfaces: Such as oceans, seas, lakes, rivers, and ponds.
3. Man-made surfaces: Such as roads, buildings, bridges, and fields.

  (d) Write any two differences between mountains and hills.

Two differences between mountains and hills:

1. Height and elevation: Mountains are generally taller and have higher elevations compared to hills. Mountains often have steep slopes and reach higher altitudes, while hills are smaller and less steep.
2. Formation: Mountains are formed through tectonic forces, such as the collision of tectonic plates or volcanic activity, resulting in large, rugged landforms. Hills, on the other hand, are typically formed through erosion and are characterized by gentler slopes.

  (e) What is hydrosphere? What forms are included in this?

Hydrosphere refers to the total sum of water on Earth, including all forms of water bodies. It includes:

1. Oceans, seas, and gulfs: Large bodies of saltwater covering a significant portion of the Earth's surface.
2. Lakes and ponds: Bodies of water that are smaller than oceans and contain freshwater.
3. Rivers and streams: Moving bodies of water that flow from higher elevations to lower elevations.
4. Glaciers and ice caps: Masses of ice and snow found in polar regions and high mountains.

  (f) What is atmosphere?

Atmosphere is the layer of gases that surrounds the Earth. It is held in place by the Earth's gravitational pull and plays a crucial role in supporting life. The atmosphere acts as a protective shield, regulates temperature, and transports moisture and gases between different regions of the Earth.

  (g) What is the atmosphere made of?

The atmosphere is primarily made up of several gases, including:

1. Nitrogen (78%): The most abundant gas in the atmosphere.
2. Oxygen (21%): Essential for respiration and combustion.
3. Trace gases: These include carbon dioxide (CO2), methane (CH4), ozone (O3), water vapor (H2O), and other gases in small concentrations.

Weather

*. Write the answers to the following questions:

  (a) What is weather?

Weather refers to the atmospheric conditions at a particular place and time, including temperature, humidity, precipitation, wind speed and direction, cloud cover, and atmospheric pressure. It describes the day-to-day variations in the state of the atmosphere.

  (b) What is weather forecast?

Weather forecast is a prediction or estimation of future weather conditions based on scientific analysis of current weather data and the use of computer models. It provides information about expected temperature, precipitation, wind patterns, and other atmospheric conditions for a specific location or region over a given period of time.

  (c) Why is weather forecasting important?

Weather forecasting is important for several reasons:

1. Safety and protection: Accurate weather forecasts help people prepare for severe weather events such as storms, hurricanes, or blizzards, allowing them to take necessary precautions and protect themselves and their property.
2. Planning and decision-making: Weather forecasts assist various sectors like agriculture, transportation, construction, and tourism in making informed decisions. Farmers can plan their crop planting and harvesting based on weather conditions, airlines can adjust flight schedules, and event organizers can plan outdoor activities accordingly.
3. Resource management: Industries that depend on weather conditions, such as renewable energy (wind and solar power) and water resource management, rely on accurate weather forecasts to optimize their operations and utilize resources effectively.
4. Climate monitoring: Weather forecasts contribute to long-term climate monitoring and research, aiding in the study of climate change patterns and trends.

  (d) How many types of clouds are there and what are they?

There are three main types of clouds:

1. Cirrus clouds: These are high-altitude clouds that appear thin, wispy, and white. They are composed of ice crystals and are often associated with fair weather conditions.
2. Cumulus clouds: Cumulus clouds are characterized by their fluffy and puffy appearance with a flat base and rounded top. They are typically found at lower altitudes and can indicate fair weather or the potential for showers or thunderstorms.
3. Stratus clouds: Stratus clouds form as flat, uniform layers that cover the sky. They are usually gray in color and can bring overcast or drizzly conditions.

  (e) Distinguish between cirrus and stratus.

The main differences between cirrus and stratus clouds are:

• Appearance: Cirrus clouds are thin and wispy, appearing as delicate filaments or fibrous strands, while stratus clouds are flat and layered, resembling a uniform sheet or blanket.
• Altitude: Cirrus clouds are high-altitude clouds found at elevations above 20,000 feet (6,000 meters), while stratus clouds are typically lower-altitude clouds, forming below 6,500 feet (2,000 meters).
• Weather indication: Cirrus clouds are often associated with fair weather, while stratus clouds are usually indicative of overcast or drizzly conditions.

  (f) Which means of communication are used in weather forecasting?

Various means of communication are used in weather forecasting, including:

1. Weather instruments: Meteorologists use instruments such as barometers, thermometers, anemometers, and rain gauges to collect data on temperature, pressure, wind speed, and precipitation.
2. Weather satellites: Satellites equipped with weather monitoring instruments capture images and data from space, providing a global perspective of weather patterns.
3. Weather radar: Radar systems detect precipitation, measure its intensity, and track its movement. This information is crucial for predicting the path and intensity of storms.
4. Weather models: Computer models use mathematical equations and data inputs to simulate and predict weather patterns. These models analyze current weather data and project future conditions.

  (g) Write an essay on your favorite weather.

Essay on my favorite weather:

My favorite weather is a sunny day with a gentle breeze. It is a day when the sky is clear, painted in a brilliant blue, and the sun shines brightly, casting a warm glow on everything it touches. The gentle breeze whispers through the air, creating a soothing sensation and carrying with it the scent of blooming flowers and freshly cut grass.

d. Write the answers to the questions given below:

  (a) What is flood?

Flood refers to the overflow of water onto normally dry land, usually caused by heavy rainfall, melting snow, dam failure, or tidal forces. It leads to an increase in the water level of rivers, lakes, or oceans, resulting in the submergence of surrounding areas.

  (b) Write the causes of floods.

Causes of floods include:

1. Heavy rainfall: Excessive rainfall over a short period can overwhelm drainage systems and cause rivers to overflow their banks.
2. Melting snow and ice: Rapid snowmelt or the melting of glaciers can contribute to increased water runoff, leading to flooding.
3. Dam failure: Failure or breach of dams or levees can release large volumes of water downstream, causing destructive floods.
4. Tropical storms and hurricanes: These weather systems often bring intense rainfall and storm surges, leading to widespread flooding in coastal and low-lying areas.
5. Urbanization and deforestation: The alteration of natural drainage patterns due to urban development and deforestation can exacerbate the risk of flooding by reducing the land's ability to absorb and retain water.

  (c) What measures should be taken to prevent landslides?

Measures to prevent landslides include:

1. Proper land-use planning: Identifying areas prone to landslides and avoiding construction or development in such high-risk zones.
2. Slope stabilization: Implementing engineering measures such as terracing, retaining walls, and slope reinforcement techniques to stabilize slopes and prevent soil erosion.
3. Afforestation: Planting trees and vegetation on slopes can help bind the soil, enhance its stability, and reduce the risk of landslides.
4. Drainage systems: Constructing effective drainage systems to control water runoff and prevent excessive water accumulation that can trigger landslides.

  (d) What is the reason for landslides not occurring on steep land planted with trees?

Landslides are less likely to occur on steep land planted with trees because the roots of trees bind the soil together, providing stability to the slope. The roots help in reinforcing the soil and prevent erosion, reducing the chances of landslides.

(e) How do communicable diseases spread due to floods?

Floods can contribute to the spread of communicable diseases through various means:

1. Contaminated water: Floodwaters can become contaminated with sewage, chemicals, and other pollutants, leading to the contamination of drinking water sources. This can result in the spread of waterborne diseases such as cholera, typhoid, and hepatitis A.
2. Displacement and overcrowding: Flooding often displaces people from their homes, forcing them to seek refuge in crowded shelters or temporary settlements. Close proximity and inadequate sanitation facilities in these settings increase the risk of transmitting diseases like respiratory infections, diarrhea, and vector-borne diseases.
3. Disruption of healthcare services: Floods can damage healthcare infrastructure, interrupt access to medical care, and hamper disease surveillance and control efforts, leading to increased vulnerability to diseases.

  (f) What is cold wave?

A cold wave refers to a weather phenomenon characterized by a rapid and significant drop in temperature in a specific region. It often brings frigid air masses and chilly winds, resulting in extremely low temperatures.

  (G) What effect does cold wave cause?

Cold waves can have several effects, including:

1. Health risks: Exposure to extremely cold temperatures can lead to hypothermia, frostbite, respiratory problems, and exacerbation of existing medical conditions.
2. Crop damage: Cold waves can harm agricultural crops and vegetation, causing frost damage and reducing yields.
3. Disruption of infrastructure: Cold waves can impact transportation systems, power supply, and other critical infrastructure, leading to disruptions in daily life.

  (h) What measures should be taken to avoid cold waves?

Measures to avoid cold waves include:

1. Staying indoors: Minimize outdoor activities during extremely cold weather and seek shelter in well-insulated buildings.
2. Dressing appropriately: Wear warm and layered clothing, including hats, gloves, scarves, and insulated footwear, to protect against the cold.
3. Heating arrangements: Ensure proper heating in homes and workplaces to maintain a comfortable temperature.
4. Monitoring weather forecasts: Stay updated on weather forecasts and advisories to take necessary precautions and follow any safety recommendations provided by authorities.

  (f) What are the safety measures to be taken in the event of a storm?

Safety measures during a storm include:

1. Seek shelter: Move to a safe location, preferably an interior room or a basement, away from windows and doors.
2. Stay informed: Listen to weather updates and warnings through radios, TVs, or weather alert systems.
3. Avoid electrical appliances: Unplug electrical equipment to prevent damage from power surges.
4. Emergency supplies: Keep essential supplies such as food, water, batteries, flashlights, and a first aid kit readily available.

(j) When Rita returned home from school, her neighbor's house was on fire

who is What can be done to reduce further damage caused by fire in such a situation?

Measures to be taken?

In the event of a fire, to reduce further damage, the following measures can be taken:

1. Call emergency services: Immediately inform the fire department about the fire to ensure prompt response and assistance.
2. Evacuate safely: If it is safe to do so, evacuate the area and ensure that everyone is out of harm's way.
3. Alert neighbors: Inform nearby residents about the fire to help them take necessary precautions and evacuate if required.
4. Use fire extinguishers: If trained and equipped, attempt to extinguish small fires using appropriate fire extinguishers, following safety protocols.
5. Prevent spreading: Close doors and windows to limit the oxygen supply to the fire, which can help contain its spread.
6. Follow emergency plans: If there is a pre-established emergency plan, follow the designated evacuation routes and assembly points.
7. Cooperate with authorities: Follow instructions from firefighters and emergency responders to ensure a coordinated and effective response to the fire.