NCERT Solutions for Class 5th The World Around Us Chapter 7 Closing questions — Let us reflect

The whole day's routine would change. Nothing that runs on a wire would work — no fan, no lights after dark, no fridge, no water pump, no TV, no charged phone.

Because solar and wind energy do not pollute the air, and they never run out. Coal makes a lot of smoke and harmful gases, and one day it will be finished.

Two clear examples: a battery, and our own body.

1. A battery. A torch cell, a mobile phone battery or the battery of an e-rickshaw holds energy inside it. Nothing happens until you switch on. Then the stored energy comes out and the torch lights, the phone rings, the rickshaw moves. When the store is finished, the battery must be charged or changed.
2. Our own body. We eat now and the body keeps some of that energy for later. That is why we can still walk and run even if we miss one meal — the body is spending what it saved.

Other everyday stores of energy you can add:

The one thing I can do is switch off every light and fan when I leave a room. It costs nothing, it takes one second, and it saves electricity every single day.

Sample answer: “In my house I have made it my own job. Whenever I leave a room I look back at the switchboard before I step out. If the fan or the light is on and nobody is there, I switch it off. I also check all the rooms once before we go out anywhere. In one month our electricity bill came down, and my father said it was because of my checking.”

Other good things to do, if you want to add more:

Ask the owner or the driver: “How many kilometres does it give in one litre?” That number is called the mileage. To compare vehicles, simply put their mileage numbers side by side — the one that gives more kilometres per litre uses less fuel for the same journey.

How to find out:

1. Choose four or five vehicles you can actually ask about — the family scooter, a neighbour's car, an auto, the school bus, a tractor.
2. Ask the owner two things: how many litres of fuel go in, and how far the vehicle runs on that.
3. Work out the kilometres for one litre by dividing.
4. Write the answers in a table.

Sample answer — what my table looked like:

These are only sample figures. Write the real numbers you are told.

How to compare them fairly. Three fair ways:

1. Kilometres per litre. Bigger is better. The motorcycle wins.
2. Fuel for the same journey. Fix a distance, say 100 km, and work out the litres each vehicle needs. Smaller is better.
3. Fuel per person. This is the fairest of all. A bus gives only 5 km per litre, but it carries 50 people. Work it out: for 100 km the bus needs 20 litres, so that is 20 ÷ 50 = 0.4 litre for each person. The car needs 5.6 litres and carries perhaps 4 people, so that is 5.6 ÷ 4 = 1.4 litres for each person. So the bus is more than three times better per person.

Here are three, written the way the book shows. The first is the book's own example.

Many more, if you want to make a longer list:

A clean energy home does three things: it makes its own clean energy, it uses as little energy as it can, and it uses the Sun and the breeze directly instead of machines.

Sample answer — my clean energy home

1. Making our own clean energy

• Solar panels on the roof, facing the Sun, making electricity for the lights, the fan and the TV.
• A solar water heater on the roof, so no geyser is needed.
• A solar cooker in the courtyard for rice, dal and vegetables on sunny days.
• A small windmill on the terrace to add electricity on windy days.
• A solar street light at the gate that charges all day and lights up by itself at night.

2. Using less

• LED bulbs everywhere — the same light for much less electricity.
• Big windows and a skylight so no bulb is needed in the daytime.
• A clothes line in the courtyard, so the Sun and the wind do the drying.
• Switches placed where a child can reach them, so lights are actually switched off.

3. Keeping the house comfortable without machines

• Thick walls and a shaded verandah, so the rooms stay cool in summer and warm in winter — the way traditional Indian houses were built.
• Windows on two opposite walls, so the breeze blows right through.
• Trees on the sunny side for shade, and a courtyard in the middle for light and air. This is what Vaastu Shastra has always advised — placing rooms, doors and windows to make the best use of sunlight, wind and heat.
• A rainwater pipe from the roof to a tank, so the pump runs less.

An energy diary is a record of every time you used energy in one day. Keep a small notebook with you and make a mark each time. At the end of the day, count.

How to make it:

1. Rule three columns in your notebook: Time, What I did, Source of energy.
2. Write a line every time you switch something on, ride in something, or eat something.
3. At the end of the day, count how many times each source was used.
4. Write one line at the bottom: what will I change tomorrow?

Sample answer — My Energy Diary, Monday

My count for the day

What I learnt, and what I will change: I used electricity more than anything else — six times out of thirteen. Two of those were not really needed: the fan stayed on in my room after I left it, and the tube light burned in the afternoon when there was plenty of daylight. Tomorrow I will switch off before leaving the room and open the curtains instead of the light. And I will try to walk to more places, because walking runs on food and makes no smoke at all.