CLASS V // TWAU // SEVENTH CHAPTER // 

Topic-  Energy - How Things Work

SUMMARY NOTE:-

What is Energy?

·      Energy is the ability to do work.

·      Energy is what makes things move, light up, produce sound, do work and change temperature.

·      We see energy in action when food cooks, fans move, bulbs glow, or water becomes hot or cold.

Different Forms of Energy:-

Type                                        Examples

Kinetic energy        Air moving a balloon rocket; fan moving air

Sound energy    Rubber band guitar producing sound when plucked

Heat energy               Sun heating water; cooking food

Light energy              Sunlight; electric bulb

Sources of Energy:-

Food Gives energy to humans & animals to work and move.

Fuel (petrol, diesel, LPG, wood, coal) used in vehicles & cooking.

Electricity runs Lights, fans and other machines.

Sun, wind & water (clean energy) - Solar panels, windmills, water wheels

 Energy in Living Things:-

• Humans and animals get energy from food.
• When we don’t eat, we feel tired; when we eat, we feel active and ready to work or play.
• Our brain uses energy even when we sit quietly, sleep or think.
• Animals like dogs, birds, and fish also need food energy to run, fly, swim, find food and protect themselves.

Energy from Fuels:-

• Vehicles like cars and scooters need fuels such as petrol and diesel to move.
• In homes, fuels like LPG (cooking gas), wood or coal are used for cooking.
• Burning too much wood or coal creates smoke and air pollution, so they should be used carefully.
• In a diya, oil acts as a fuel and makes the flame burn longer than a dry wick.

Electricity:-

• Many things in our homes and schools run on electricity – fans, lights, TVs, coolers, refrigerators, mixers, etc.
• Electricity can be used for movement (fans), light (bulbs), sound (TV, music systems), heat (iron, geyser) and cooling (fridge, cooler).
• Our daily life and many factories/industries depend on electricity to run machines and make things like clothes, toys, books and packed food.

Safe Use of Electricity:-

·      Never touch wires or parts of electrical devices when they are plugged in.

·      Never put fingers, pens or sticks into electric sockets.

·      Stay away from broken wires or fallen electric poles and inform an adult.

·      Do not play near electric boxes or transformers.

·      If something looks unsafe, never try to fix it yourself – always call an adult.

Clean Energy:-

Electricity generated using natural sources of energy like wind, water or the Sun’s energy, does not pollute the planet with smoke or waste, and is called clean energy.

Examples of using clean energy: Solar panels for electricity, Windmills to generate power, Water wheel turbines, Drying clothes in the sun

Energy Efficiency:-

Energy efficiency means using less energy to do the same work. This helps save resources and reduce waste. For example, using LED bulbs instead of incandescent or fluorescent bulbs gives the same amount of light, but uses less electricity.

Stored Energy:-

• Our body stores extra energy from food, so we can still walk or run even if we skip a meal.
• Batteries store energy and help torches, toys and remotes work.
• Stored energy can be used later when it is needed.

Using and Saving Energy Wisely:-

• Energy is all around us – in food, fuels, electricity, Sun, wind and water.
• We should choose clean energy sources like solar and wind energy whenever possible.
• Simple ways to save energy:
  – Switch off lights, fans and TVs when not in use.
  – Use LED bulbs to save electricity.
  – Use sunlight and fresh air instead of lights and coolers whenever possible.
  – Use public transport, walk or cycle for short distances to save fuel.
• Using and saving energy wisely keeps our Earth cleaner and healthier.

Important points:-

Ø The Flying Snake, living in Indian forests can glide through the air by flattening its body.

Ø The Bhadla Solar Park in Rajasthan is one of the largest solar power plants in the world.

Ø Cochin International Airport in Kerala is the world’s first airport to be entirely powered by solar energy.

Ø Traditional houses in India had small windows and thick walls. This kept the house cool in summer and warm in winter.

Ø In hilly areas, watermills called gharaats use flowing water to grind grains.

Ø The Sun is the main source of energy for life on Earth.

Ø Our body stores energy for future use. We can still run or walk even if we skip a meal because our body uses the stored energy. We use torches or toys that use batteries. Batteries contain stored energy.

Ø Vaastu Shastra, the ancient Indian system of design and architecture, helps plan buildings in harmony with nature. It guides the placement of rooms, doors, and windows to make the best use of natural energy like sunlight, wind and heat. Open spaces like courtyards and well-placed openings help homes stay bright, airy and reduce the use of energy in different seasons.

Ø Some plants in deserts open only at night to save water and energy.

  A. FILL IN THE BLANKS:-

a)   Energy makes things move and work.

b)   Energy is what makes things move, light up, produce sound and do work.

c)    We get energy from the food we eat because food is a source of energy for living beings.

d)   Vehicles like cars and scooters run on fuels such as Petrol and diesel.

e)   Cooking gas / LPG is used in many homes for cooking and heating water.

f)     Burning coal creates smoke and harmful gases that pollute the air.

g)   Sun, wind and water are natural sources that can be used to generate clean energy.

h)   Electricity produced from natural sources such as sun, wind or water is called clean energy.

i)      A pinwheel rotates with the help of wind energy.

j)     Using LED bulbs helps save electricity because they use less energy.

k)    Batteries store electrical energy for later use.

B. Column Matching :-

 

1. Match the followings:

Column A	Column B
1. Sun	Heat and light
2. Petrol / Diesel	Runs a car
3. Battery	Stores energy
4. Fan	Movement
5. Windmill	Wind energy

C. Complete this analogy:-

1.               Food : Humans :: Petrol : Vehicles 2.                Sunlight : Solar Panels :: Wind : Windmill 3.               Fan : Movement :: Bulb :  Light 4.              Coal : Polluting Energy :: Sun : Clean energy 5.              Clothes drying : Sun :: Ship sails : Wind

D.  Write 'T' for True and 'F' for False statements:-

• 1.   Energy is needed to make things move, produce sound or give light. True
• 2.   Animals do not need energy to move or find food. False
• 3.   Petrol and diesel are fuels used in vehicles. True
• 4.   Burning coal does not cause pollution. False
• 5.   The Sun, wind and water are clean sources of energy. True
• 6.   Electricity is never dangerous and can be touched with wet hands. False
• 7.   Solar panels change sunlight into electricity. True
• 8.   Batteries store energy to be used later. True
• 9.   Using LED bulbs helps in saving electricity. True

E. Differentiate:-

1. Renewable Energy and Non-renewable Energy

Renewable Energy	Non-renewable Energy
Comes from natural sources like Sun, wind and water.	Comes from fuels like coal, petrol and diesel.
Does not cause pollution.	Causes pollution when burnt.
Will never run out.	Limited in amount and will finish one day.
Example: Solar panels, windmills.	Example: Thermal power using coal.

2. Solar Energy and Wind Energy

Solar Energy	Wind Energy
Energy from the Sun’s heat and light.	Energy produced by moving air/wind.
Captured using solar panels.	Captured using windmills/wind turbines.
Used for cooking, heating, lighting, drying clothes.	Used to run windmills and generate electricity.

3. Electricity and Fuel

Electricity	Fuel
Runs electrical appliances like fan, TV, fridge and lights.	Runs vehicles and is used for cooking.
Can be produced by clean sources like Sun, wind and water.	Produces smoke and pollution when burnt.
Example: Power from solar panels.	Example: Petrol, diesel, coal, LPG.

4. LED Bulb and Normal Bulb

LED Bulb	Normal Bulb
Uses less electricity and saves energy.	Uses more electricity and wastes energy.
Energy-efficient and lasts longer.	Less efficient and shorter life.

5. Battery and Electricity (direct)

Battery	Electricity
Stores energy to use later.	Supplied continuously from power stations.
Used in toys, torches and remote controls.	Runs appliances like TV, fridge, AC, fan.

 

 

 

 

 

 

 

F. Very Short Answer Questions

1. Define energy.       

Ans - Energy is what makes things move, produce sound, light up, or change temperature.

2. What is the main source of energy on Earth?  

Ans - The Sun.

3. Name a clean source of energy.      

Ans - Solar energy / Wind energy / Water energy

4. Name any two sources of energy.

Answer: Sun and wind.

5. What do vehicles need to run?

Answer: Fuel like petrol or diesel.

6. What does a fan need to work?

Answer: Electricity.

7.Name a fuel used for cooking.

Answer: LPG (cooking gas).

8.What type of energy does a pinwheel use?

Answer: Wind energy.

9.What stores energy in a torch?

Answer: Battery.

10.Name one clean source of energy.

Answer: Solar energy.

11.What is electricity produced from natural sources called?

Answer: Clean energy.

12.Which bulb uses less energy—LED or normal bulb?

Answer: LED bulb.

13.Give one use of solar panels.

Answer: To generate electricity.

 

 

 

 

 

 

 

G. Short Answer Questions

Q1:  Give two examples where you have seen energy being stored?

Ans: Two examples where energy is stored are: 1. Batteries of mobile phones and toys store electrical energy, 2. Water stored in a dam stores potential energy.

Q2:  Why do we need food?

Ans: Food gives energy to our body to move, work, play and stay active.  

Q3. What is electricity used for in our homes?

Ans : Electricity is used to run fans, lights, TV, refrigerator, etc., for movement, cooling, heating, light and sound.

 

 

H. Long Answer Questions

Q1: Draw or make a simple plan of a ‘clean energy home’ that uses solar, wind or any such source of energy.

Q2. How can we use electricity safely?

    Ans :

Ø Never touch wires or parts of electrical devices when they are plugged in.

Ø Never put fingers, pens or sticks into electric sockets.

Ø Stay away from broken wires or fallen electric poles and inform an adult.

Ø Do not play near electric boxes or transformers.

Ø If something looks unsafe, never try to fix it yourself – always call an adult.

I. Application/Thinking Questions

Q1: Why do people in Himachal Pradesh keep their cattle on the ground floor of their houses ?

Ans: In some places of Himachal Pradesh, Uttarakhand and Ladakh, people often keep their cattle on the ground floor of their houses, while the family lives on the floor above. The heat from the animals helps keep the rooms warm during the winter. This is a clever way to stay warm in cold regions without using extra firewood or electricity.

Q2: What will happen if there is no electricity in your house for a day?
Ans: If there is no electricity in the house for a day, daily activities are disturbed. Lights, fans, TV, refrigerator and internet stop working, and phones cannot be charged. It becomes difficult to study at night, food may spoil, and life becomes uncomfortable. However, people may spend more time talking, reading or playing together.

Q3. Why is it better to use solar or wind energy instead of coal?

Ans : It is better to use solar or wind energy instead of coal because they are clean and renewable sources of energy. They do not cause air pollution or release harmful gases like coal does, which helps reduce global warming. Also, solar and wind energy will never run out, while coal is limited and will get exhausted one day.

Q4. What is the one thing you can do at home to save energy?

Ans : One thing I can do at home to save energy is to switch off lights, fans and other electrical appliances when they are not in use. This reduces electricity waste and saves energy.

 

HOMEWORK :-

1. Find out how many kilometres a vehicle travels per litre of petrol or diesel. Ask about different vehicles. How will you compare them?

 2. Look around your home or classroom. List any three objects that use energy and mention their source of energy.

 For example: Object; Fan → Energy Source: Electricity

3. Make ‘my energy diary’ for one day, record the number of times you have used the electricity fuel and so on.

 

                 Honesty is the best policy.