Forms of Energy Around Us ഊർജരൂപങ്ങൾ
Before the chapter defines energy exactly, it helps to notice how much of it is around you: electricity in the wires, heat in the dosa tawa, sound from the temple chenda, chemical energy in your breakfast, light from the Sun. This page names the forms of energy, shows how machines in a Kerala home change one form into another, traces almost all of it back to the Sun, and explains why energy and work, unlike force, have no direction.
- Forces and displacement as arrows (page 1).
- The joule as a unit (page 2).
1. What is energy?
Whenever something happens – a bus moves, water heats up, a bulb glows, a bell rings – energy (ഊർജം) is at work. Energy is what lets an object or a system do work: push, pull, lift, move, heat or light something. On page 7 your textbook gives the exact definition: energy is the capacity to do work. Energy is measured in the same unit as work, the joule (J).
The chapter opens at a dam: “How does the water get so much energy?” By the end of this page you will already be able to say where that energy originally came from. Page 10 finishes the story.
2. The forms of energy
Energy comes in many forms (ഊർജരൂപങ്ങൾ). These are the ones your textbook names:
⚡ Electrical energy വൈദ്യുതോർജം
Energy carried by an electric current in wires. It runs fans, motors, TVs and phone chargers. KSEB supplies it to every home.
⚙️ Mechanical energy യാന്ത്രികോർജം
Energy of moving things (a running bus, a falling coconut) and of things that are raised or stretched (water in a reservoir, a drawn bow). Pages 7–8 split it into potential and kinetic energy.
🔥 Heat energy താപോർജം
Energy that makes things hotter: a dosa tawa, an iron box, the warm motor of a mixer.
🧪 Chemical energy രാസോർജം
Energy stored in food, firewood, LPG, petrol and in the dry cells of a torch. It is released by chemical reactions – burning, digestion, cell reactions.
💡 Light energy പ്രകാശോർജം
Energy carried by light: from the Sun, an LED bulb, a nilavilakku flame or a phone screen.
🔔 Sound energy ശബ്ദോർജം
Energy carried by vibrations through air: a temple bell, the chenda at a festival, a loudspeaker.
☀️ Solar energy സൗരോർജം
Energy from the Sun, reaching us as light and heat. Rooftop solar panels turn it into electricity.
⚛️ Nuclear energy ആണവോർജം
Energy stored inside the centre (nucleus) of atoms. It powers the Sun itself and nuclear power stations such as Kudankulam in Tamil Nadu.
Pick the main form of energy the object has (or gives out). There are ten objects; your score is counted at the top right.
3. Energy changes form – energy chains at home
Energy is never used up in the sense of disappearing: a machine takes in energy in one form and gives it out in other forms. This is called energy transformation (ഊർജപരിവർത്തനം). Most machines give out some energy we want (useful) and some we do not want, usually heat and sound (wasted). That is why a mixer grinder gets warm and noisy.
Green boxes are useful outputs; red dashed boxes are wasted energy. Whatever goes in comes out – the total amount of energy stays the same (page 9: the law of conservation of energy).
Worked example 1 · The energy chain of a torch
Q. Write the energy changes that take place when a torch is switched on.
Start with what is stored in the dry cells. What flows through the wire? What does the bulb give out – and does it get warm?
4. Where does it all come from? The Sun
Follow almost any energy chain backwards and you reach the Sun. Plants store sunlight as chemical energy in food; ancient plants became coal and petroleum; the Sun lifts water into the clouds that fill our reservoirs. Step through the chains below. (Nuclear energy is one of the few exceptions – and even the Sun runs on nuclear energy.)
The Sun is the main source of energy on Earth. Its light energy becomes chemical energy in plants (food, wood, and over millions of years coal and petroleum), drives the water cycle that fills our dams, makes winds blow, and is turned straight into electricity by solar panels.
5. Quantities with and without direction: scalars and vectors
Some quantities need a direction to be complete. “Push the trolley with 95 N” is not enough – push it which way? Such quantities are vector quantities (സദിശ അളവ്): force, displacement, velocity, acceleration, weight. Others are complete with just a size (a number and a unit): mass, time, distance, speed, and – importantly for this chapter – work, energy and power. These are scalar quantities (അദിശ അളവ്).
Scalars add like ordinary numbers: 18 J of work plus 15 J of work is always 33 J, whichever directions the pushes were in. Vectors do not: walk 4 m east and 3 m north and you are only 5 m from the start.
A 2 N push acts in the direction of each move (east, then north). The work in each part is 2 N × the distance of that part. The total work is just their sum. The displacement (blue arrow) is measured straight from start to finish, so it is shorter than the path whenever the box turns a corner. (Each grid square is 1 m.)
Worked example 2 · Adding works in different directions
Q. A box is pushed with a force of 2 N towards the east and moves 4 m east. Then a force of 2 N towards the north moves it 3 m north. Find the total work done.
Find the work in each part with W = F × s (force and displacement in the same direction each time). Work is a scalar, so just add.
Work, energy and power are scalars (അദിശ അളവ്). Force and displacement are vectors (സദിശ അളവ്). Work and energy also share the same unit, the joule – two of the “similarities of work and energy” on page 9.