What energy is and its forms
In a kitchen, flames burn, mixers whirr, lights glow and food gets hot. What makes all this happen?
Energy is what makes things move, shine, make sound, do work and change temperature. We see it as movement, light, sound and heat. A balloon rushing forward as air escapes, a plucked rubber band that vibrates to make sound, and water warming in the Sun are simple examples.
In the figure: Energy shows up as movement, light, sound and heat.
Key point 1: Seeing energy at work
- Easy : Air rushing out pushes a balloon forward.
- Medium : A plucked rubber band vibrates and makes sound.
- Exam-type : Water in sunlight becomes warmer than water in shade.
Key point 2: Forms we notice
- Easy : Movement: running, rolling, flying.
- Medium : Light and heat: lamps, the Sun, fire.
- Exam-type : Sound: music, a bell, a horn.
Energy is not seen directly; we see what it does.
Thinking energy is only electricity.
Energy makes things Move, Shine, Sound, Heat. Memory clue: "MSSH".
Spot the difference
| Form | Example | What happens |
|---|---|---|
| Movement | balloon rocket | moves forward |
| Sound | rubber-band guitar | vibrates |
| Heat | water in sun | gets warm |
Practice questions
- 1What is energy?
- 2Name two forms of energy.
- 3What makes the balloon move forward?
- 4What makes sound in a rubber-band guitar?
- 5Which cup of water gets warmer, in sun or shade?
- 6Name one thing that gives light.
- 7Give one example of heat energy at home.
- 8How can you make the balloon rocket move faster?
Show answers (try them yourself first)
- 1What makes things move, shine, sound, work and heat.
- 2Any two of movement, light, sound, heat.
- 3Air rushing out.
- 4Vibrating rubber bands.
- 5The one in the sun.
- 6Sun, bulb or lamp (any one).
- 7A stove or a hot iron.
- 8Blow more air or use a smoother string.
Sources of energy: food, fuel, electricity
Why do we feel tired when hungry and active after eating? And what makes a scooter go?
Living things get energy from food, so food is our fuel. Vehicles run on fuels such as petrol and diesel; cooking gas, wood and coal are fuels used for cooking. In a diya, oil is the fuel. Electricity gives movement, sound, light and heat to fans, TVs, bulbs and heaters. Burning wood or coal makes smoke and pollution.
In the figure: Food, fuel and electricity keep us and our machines going.
Key point 1: Food and fuel
- Easy : Food gives energy to humans and animals to run, fly or think.
- Medium : Petrol and diesel move vehicles; oil keeps a diya burning.
- Exam-type : Burning wood or coal creates smoke, so use them carefully.
Key point 2: Electricity
- Easy : Electricity can give movement, sound, light and heat.
- Medium : Many machines in factories run on electricity.
- Exam-type : Most electricity today comes from burning coal, which pollutes the air.
Even our brain uses energy while we sit or sleep.
Thinking food is not a source of energy.
Food for us, fuel for machines. Memory clue: "Food-Fuel-Flow (electricity)".
Spot the difference
| User | Source | Example |
|---|---|---|
| Humans | food | running |
| Vehicle | petrol / diesel | scooter |
| Fan | electricity | blowing air |
Practice questions
- 1Where do living things get energy from?
- 2Name one fuel used by vehicles.
- 3Name one fuel used for cooking.
- 4In a diya, what is the fuel?
- 5Name two things in your home that run on electricity.
- 6Why is burning coal harmful?
- 7What happens to our body if we do not eat?
- 8Why does a diya with oil burn longer than a dry wick?
Show answers (try them yourself first)
- 1From food.
- 2Petrol or diesel.
- 3Cooking gas, wood or coal (any one).
- 4Oil.
- 5Fan and bulb (any two).
- 6It makes smoke and pollutes the air.
- 7We feel tired and weak.
- 8The oil keeps feeding the flame as fuel.
Clean energy from Sun, wind and water
Clothes dry on a sunny line, a pinwheel spins in the breeze and a stream turns a wheel. Nature is doing work for free.
The Sun is the main source of energy for life on Earth. Solar panels turn sunlight into electricity, windmills spin in wind to make electricity, and flowing or falling water can also generate it. Electricity made this way gives no smoke or waste, so it is called clean energy. Old ships used sails to travel using wind energy.
In the figure: Sun, wind and water give energy without smoke.
Clean energy from Sun, wind and water
In the app you can move this figure with your finger.
Open in the appKey point 1: Three clean sources
- Easy : Sun: heat and light, and electricity from solar panels.
- Medium : Wind: spins windmills and pushes sails.
- Exam-type : Water: turns water wheels, traditional watermills and turbines.
Key point 2: Why clean energy
- Easy : It does not pollute the air with smoke.
- Medium : Sunlight reaches Earth every day and is free to use.
- Exam-type : Hilly areas use flowing water in watermills to grind grain.
Even drying papad or clothes in the Sun uses clean energy.
Thinking solar panels give heat only.
Clean energy = Sun, Wind, Water (SWW). Memory clue: "Sun-Wind-Water – Smoke-free".
Spot the difference
| Source | Device | Use |
|---|---|---|
| Sun | solar panel | electricity |
| Wind | windmill | electricity |
| Water | water wheel | turning machines |
Practice questions
- 1What is clean energy?
- 2Name three clean sources of energy.
- 3What does a solar panel do?
- 4What does a windmill do?
- 5How did old ships use wind?
- 6Which source is the main source of life on Earth?
- 7Give one everyday use of the Sun's energy.
- 8Why is clean energy better than coal?
Show answers (try them yourself first)
- 1Energy that does not pollute.
- 2Sun, wind and water.
- 3Turns sunlight into electricity.
- 4Spins in the wind to make electricity.
- 5Sails caught the wind.
- 6The Sun.
- 7Drying clothes or papad.
- 8It gives no smoke or harmful gases.
Safe use and saving of energy
A broken wire on the road, a fan running in an empty room – small actions around electricity matter.
Electricity is useful but dangerous if used carelessly. Never touch wires, put things in sockets or play near transformers; stay away from broken wires and tell an adult. Energy efficiency means doing the same work with less energy, e.g. an LED bulb gives the same light with less electricity. Our body and a battery both store energy for later use.
In the figure: Be careful with electricity and use only what you need.
Key point 1: Safety rules
- Easy : Do not put fingers or pens into sockets.
- Medium : Stay away from fallen poles and broken wires, and tell an adult at once.
- Exam-type : Do not play near electric boxes or transformers.
Key point 2: Saving energy
- Easy : Switch off lights and fans when not needed.
- Medium : Use LED bulbs: same light, less electricity.
- Exam-type : Traditional houses with thick walls and small windows stay cool and warm without extra energy.
Only adults should repair electrical things.
Thinking it is fine to fix a broken wire if the switch is off.
Electricity safety: Don't touch, Stay away, Tell. Memory clue: "DST".
Spot the difference
| Action | Right or wrong | Why |
|---|---|---|
| Poking a socket | wrong | shock risk |
| Telling an adult about a fallen wire | right | keeps everyone safe |
| Using LED bulb | right | saves electricity |
Practice questions
- 1Why is electricity dangerous?
- 2What should you do if you see a broken wire?
- 3What is energy efficiency?
- 4Name a bulb that saves electricity.
- 5Where is energy stored in a torch?
- 6Why should you not play near transformers?
- 7How can you save energy at home?
- 8Which part of your body stores energy?
Show answers (try them yourself first)
- 1It can cause shocks if misused.
- 2Stay away and tell an adult.
- 3Doing the same work with less energy.
- 4LED bulb.
- 5In its battery.
- 6They carry strong electricity.
- 7Switch off unused lights and fans.
- 8The body stores energy from food.