How it's made and how it reaches you

Flick on a ceiling fan in Pune or Patna and it starts turning almost at once. Somewhere, possibly hundreds of kilometres away, a machine the size of a railway carriage is spinning 50 times a second, and a tiny share of its output has just been sent to your fan.

You have already met voltage (the push), current (the flow) and resistance (what gets in the way). This layer asks the bigger questions: where does the push come from in the first place, and how does it travel all that way without most of it being lost?

The story has three parts.

1. Making it. Almost every power station on Earth, whether it burns coal, splits uranium or catches the wind, uses the same trick discovered in 1831: move a magnet near a coil of wire and a current appears. Solar panels are the big exception.
2. Moving it. Electricity leaves the station, gets its voltage raised enormously, races across the country on tall steel towers, and is stepped down again, several times, before it reaches your street.
3. Balancing it. Electricity is hard to store in bulk, so the grid has to make exactly as much as everyone uses, second by second. The frequency of the grid, 50 Hz in India, is the tell-tale sign of whether that balance is being kept.

In 1820 the Danish scientist Hans Christian Ørsted noticed that a wire carrying current made a nearby compass needle swing. Electricity could make magnetism. The obvious question followed: could magnetism make electricity?

For years people tried and failed. They put strong magnets next to coils of wire and waited. Nothing happened. In 1831 Michael Faraday, working at the Royal Institution in London, found out why. He wound two separate coils of wire around an iron ring. When he switched on a battery connected to the first coil, a needle attached to the second coil gave a brief kick, then settled back to zero. When he switched the battery off, it kicked again, the other way.

The current in the second coil only appeared while the magnetism was changing. A steady magnet, however strong, does nothing. A changing one pushes charge.

Faraday soon showed the same thing with nothing but a bar magnet and a coil. Push the magnet into the coil and a current flows one way. Hold it still inside and the current stops. Pull it out and the current flows the other way.

He noticed three things that made the push (the induced voltage) bigger:

• Move faster. The quicker the magnetic field inside the coil changes, the bigger the push.
• Use more turns. Every loop of wire gets its own small push, and they add up. A coil of 500 turns gets 500 times the push of a single loop.
• Use a stronger magnet. More magnetic field means more field to change.

That is electromagnetic induction, and it is the heart of this whole layer. The rule in words: the induced voltage depends on how fast the magnetic field through the coil changes, multiplied by the number of turns.

A power-station generator is Faraday's magnet and coil, scaled up and organised.

• The rotor is a huge spinning electromagnet on a steel shaft.
• The stator is a stationary cylinder of heavy copper coils wrapped around the rotor.
• A turbine on the same shaft is pushed round by steam, water or wind.

As the rotor turns, its north pole sweeps past a coil, then its south pole. The field through each coil rises, falls, reverses and comes back. So the push on the charges rises, falls, reverses, and comes back. The generator naturally makes alternating current, AC.

One full turn of a two-pole rotor (one north, one south) gives one complete wave: push one way, then the other. That complete wave is called a cycle, and the number of cycles each second is the frequency, measured in hertz (Hz).

What if you want 50 Hz but your turbine prefers to turn more slowly? Add more poles. A rotor with four poles (north, south, north, south) sends two complete waves past each coil in every turn. So it only needs to spin at 1,500 rpm to make 50 Hz.

Hydroelectric generators take this idea much further. Water turbines turn slowly, so their rotors have dozens of poles arranged around a wide wheel. A 40-pole hydro generator makes 50 Hz at just 150 rpm.

Direct current (DC) pushes charge one way only. A torch cell, a phone battery and a car battery all give DC. Inside, a chemical reaction separates charge: one terminal ends up with a surplus of electrons, the other with a shortage, and the push is always from the same side. The symbol ⎓ on a charger means DC.

Alternating current (AC) keeps reversing. The mains in your home swings smoothly from pushing one way, to zero, to pushing the other way, and back, 50 complete times every second. The symbol ~ means AC.

Since each cycle contains two reversals, 50 Hz means the direction reverses 100 times a second. The electrons in your fan's wire do not travel from the power station at all; they jiggle back and forth by a tiny fraction of a millimetre. The energy travels, carried by the electric and magnetic fields along the wires.

Your phone battery can only be charged with DC, at a low voltage. So the little brick you plug into the wall does two jobs: it lowers the voltage from 230 V to around 5 V, and it rectifies the current, turning the back-and-forth AC into one-way DC. Laptops, LED bulbs, TVs and inverter ACs all contain a circuit that does the same thing inside them. Most modern electronics quietly run on DC, made from AC at the last moment.

So why not simply send DC everywhere? Because, as the next chapters show, the grid depends on transformers, and transformers only work with AC. That single fact decided the shape of the world's electricity systems.

Every power station has to answer one question: what will turn the turbine? Coal, gas, uranium, falling water and moving air are simply different answers. After the turbine, the generator is almost the same in all of them. Choose a station below to follow its chain of energy, from source to socket.

Electricity leaves a generator at a moderate voltage, is pushed up to hundreds of thousands of volts for the long trip, and is stepped down in stages as it gets closer to you. Every change of voltage happens in a transformer. Here is the typical Indian route.

Transmission wires are thick aluminium, but over hundreds of kilometres even they have some resistance, a few ohms. Current flowing through resistance heats the wire, and that heat is energy lost.

Two formulas explain everything:

• The power delivered is P = V × I. For a fixed amount of power, you can use a high voltage with a small current, or a low voltage with a large current.
• The power wasted as heat in the wire is loss = I² × R. It depends on the square of the current.

So raise the voltage 10 times and, for the same power, the current falls to one-tenth. The loss falls to (1/10)² = one-hundredth. That square is the whole reason for tall towers and enormous voltages.

A transformer is Faraday's iron ring, grown up. Two coils are wound on the same iron core, with no electrical connection between them.

1. AC flows in the primary coil. Because the current keeps changing, it makes a magnetic field that keeps changing.
2. The iron core carries that changing field through the secondary coil.
3. A changing field through a coil induces a voltage (Faraday again), so AC appears in the secondary.

Every turn of wire, on either coil, gets the same voltage per turn. So the coil with more turns has the bigger voltage:

Vs ÷ Vp = Ns ÷ Np

More turns on the secondary means a step-up transformer; fewer means step-down.

Power is how fast energy is transferred, measured in watts (W). One watt is one joule every second. For an appliance on the mains, P = V × I. A 1,500 W kettle on 230 V draws about 1,500 ÷ 230 ≈ 6.5 A.

Energy is power multiplied by time: E = P × t. Energy in joules is a very small unit for a household, so electricity companies use a bigger one: the kilowatt-hour (kWh), the energy used by 1,000 W running for one hour. On an Indian bill, one kWh is simply called one unit. One kWh equals 1,000 W × 3,600 s = 3,600,000 J, or 3.6 MJ.

A quick way to find units: watts × hours ÷ 1,000. The extend layer turns this into a full bill with real appliances and tariffs.

All the big generators across mainland India are connected to one grid, and they all spin in step, like dancers following the same beat. That beat is the grid frequency, 50 Hz.

Now picture the evening. Millions of people get home, switch on lights, fans, TVs and, in summer, air conditioners. Demand jumps. For a moment the generators are asked for more power than their turbines are supplying. Where does the extra come from? From the spinning energy of the rotors themselves. They slow down, very slightly, and the frequency dips, say from 50.00 to 49.95 Hz.

The opposite happens on a sunny, quiet Sunday afternoon: lots of solar, low demand, too much supply. The rotors speed up a touch and the frequency creeps above 50 Hz.

So frequency is the grid's pulse. Control rooms in every region watch it constantly and order stations to raise or lower output, keeping supply and demand matched every second.

Operators have a toolbox for keeping the balance:

• Forecasting. Demand follows patterns: it rises in the morning, peaks in the evening, and is higher in the heat of May than in December. Weather forecasts predict solar and wind output.
• Fast responders. Hydro and gas stations can change output within minutes. Many large thermal units are also required to respond automatically to small frequency changes.
• Storage. Pumped-storage hydro and, increasingly, large battery banks soak up surplus solar in the afternoon and give it back in the evening.
• Last resort. If frequency falls dangerously, automatic relays switch off some areas (load shedding) to save the rest of the grid from collapsing.

The hardest hour is the evening peak. Solar output fades just as homes light up, so other stations must ramp up quickly while the sun sets.

Where does India's electricity actually come from? The answer changes year by year, as solar farms spread across Rajasthan and Gujarat and wind grows in the south. The table shows approximate, rounded shares of electricity generated (energy produced, not capacity) over roughly the 12 months up to mid-2026, from published data compilations. Exact figures differ between sources and years, so treat these as a picture of the balance, not precise numbers.