Energy and electricity

25 to explore

• Watch Try it What If? Lab What if a battery had more voltage? A battery's voltage is how hard it pushes electric current around a circuit. Swap a 3-volt battery for a 9-volt one in our model and the same two bulbs carry three times the current, and each one uses nine times the power. Find out why, and why a real bulb can burn out on too much voltage.
• Watch Try it What If? Lab What if a battery wasted energy as heat? A battery's label tells you how much energy it stores. But on the way from the battery to a device, some energy always turns into heat in the wires and electronics. In our model, a 60-watt-hour battery runs a 10-watt lamp for 6 hours when nothing is lost. If 30% is lost as heat, the lamp goes dark after 4 hours 12 minutes.
• Watch Try it What If? Lab What if a battery were old and tired? Every battery has a little resistance inside it. A fresh battery has hardly any, but as a battery gets worn out, that inside resistance grows. In our model, four bulbs side by side glow at full brightness on a fresh 3-volt battery. Make the battery old and tired, and watch what happens to the bulbs and to the battery itself.
• Watch Try it What If? Lab What if a house had a tiny heater? A warm house is always leaking heat into the cold outside. A heater keeps it warm only if it can put heat back as fast as it leaks out. In our model, a 10-kilowatt heater keeps a leaky house at 20 °C on a freezing day. Swap it for a tiny 3-kilowatt heater, and the house slowly cools until it finds a new balance.
• Watch Try it What If? Lab What if a house’s heating switched off on a cold night? A warm house is always leaking heat into the cold night. If the heating stops, nothing replaces it. In our model, an insulated house at 20 °C on a 0 °C night cools to about 15 °C in 12 hours, and then more and more slowly as it gets closer to the outside temperature.
• Watch What If? Lab What if a machine could run forever? For more than a thousand years, inventors have drawn wheels and gadgets that were meant to keep turning forever with nothing to power them. None has ever worked. Follow the energy in this thought experiment to see why: energy is never made from nothing, and every moving machine leaks a little of it away as heat.
• Watch Try it What If? Lab What if a solar panel lay flat? Sunlight gives a panel the most energy when it hits the panel straight on. In London in March, the Sun stays low in the sky, so our model panel tilted at 40° makes about 1.86 kilowatt-hours in a day. Lay it flat and the slanting light spreads out: it makes only about 1.17.
• Watch Try it What If? Lab What if a switch were left open? A switch is a little gate in a circuit. Closed, it lets electric current flow all the way around the loop. Open it in our model and the loop has a gap: the current drops to zero and every bulb goes dark at once, however the bulbs are wired.
• Watch Try it What If? Lab What if a turbine caught every bit of the wind? A wind turbine slows the wind down to take some of its energy. So why not slow it all the way down and take all of it? In our model, a good turbine catches 45% of the wind's power. Push it to the very best any turbine could ever do, and you hit a wall at about 59%, called the Betz limit.
• Watch Try it What If? Lab What if a turbine had a small generator? A wind turbine's blades catch the wind, but its generator turns that spin into electricity, and every generator has a top limit called its rated power. In our model, big blades in a strong wind make about 2.13 megawatts with a large generator. Swap in a 1-megawatt generator, and the turbine can never make more than 1 megawatt, however hard the wind blows.
• Watch Try it What If? Lab What if batteries stored less energy? A battery stores a set amount of energy, and a device uses it up at a steady rate. In our model, a 60 watt-hour battery runs a 10-watt lamp for 6 hours. Shrink the battery to 15 watt hours and the same lamp goes dark after an hour and a half.
• Watch Try it What If? Lab What if bulbs were wired side by side? When two bulbs share one loop of wire, they share the battery's push and both glow dimly. Wire them side by side instead, each on its own path to the battery, and each gets the battery's full push. In our model, each bulb then glows four times as brightly. But there's a catch: the battery has to work four times as hard.
• Watch What If? Lab What if electricity traveled without wires? A wireless charging pad sends energy across a tiny gap using a changing magnetic field, and scientists have even charged a car this way. But could electricity travel everywhere without wires? Follow three paths: charging pads, energy carried by radio waves, and why wires still carry our electricity across the country.
• Watch Try it What If? Lab What if one bulb in a string broke? In a series circuit, electric current has only one path, so it must flow through every bulb in turn. Take one bulb out of our model and the path is broken: all three bulbs go dark. Then wire the same bulbs side by side and see what changes.
• Watch What If? Lab What if rivers made electricity everywhere? Falling and flowing water can spin a turbine, and a turbine can spin a generator to make electricity. That's hydropower, one of the oldest ways people have used energy. Imagine every river making electricity, then discover how dams work, why fish need a way past them, and how small water wheels can power a single farm.
• Watch Try it What If? Lab What if solar panels were near the equator? On 21 December in London, the noon Sun is only about 15° above the horizon, and it is up for less than 8 hours. In our model, a rooftop panel there makes about 0.64 kilowatt-hours that day. Move the same panel to the equator and the Sun climbs to about 67° and shines for 12 hours: the panel makes about 2.34, more than three and a half times as much.
• Watch Try it What If? Lab What if the wind blew twice as hard? A wind turbine turns moving air into electricity. In our model, a gentle 5 m/s wind lets a big turbine make about 0.15 megawatts. Double the wind to 10 m/s and it makes about 1.23 megawatts: eight times as much, because faster wind brings more air each second and each bit of air carries more energy.
• Watch What If? Lab What if the world ran on sunshine? Solar panels turn sunlight into electricity, and a 2020 World Bank study found that most countries get far more sunshine than they would need for all the electricity they use now. But the Sun sets every night, and winter days are short. Imagine a world running on sunshine and follow the big engineering puzzles: day and night, storing energy, and finding room for panels.
• Watch What If? Lab What if there were no electricity for a day? Electricity reaches your home through a giant network called the grid. Sometimes storms or faults cut it off for a while. Imagine a whole day without it: what happens to the lights and the fridge, how does the grid get electricity to you, and how do hospitals keep working when it stops?
• Watch What If? Lab What if we used heat from inside Earth? The deeper you go underground, the hotter the rocks and water get. In Iceland, hot water from underground heats most homes, and in Kenya, underground steam makes more than 40 percent of the country's electricity. Explore what would happen if we used Earth's own heat: in volcanic places like Iceland, at hot springs, and even just a few feet under your own backyard.
• Watch Try it What If? Lab What if winter were much colder? Heat leaks out of a house faster when it is colder outside. In our model, an insulated house kept at 20 °C needs about 86 kilowatt-hours of heat a day when it is 0 °C outside. Drop the outside to −20 °C and the gap doubles, so it needs twice as much: about 173 kilowatt-hours.
• Watch Try it What If? Lab What if you added more bulbs in a row? One bulb on a 3-volt battery glows brightly. Add more bulbs in a row, all on one path, and each new bulb adds resistance, so less current flows. In our model, four bulbs in a row each glow at only 6 percent of one bulb's brightness. Find out why, and how real strings of lights use this idea.
• Watch Try it What If? Lab What if you kept adding bulbs side by side? When bulbs are wired side by side, each one has its own path to the battery. Add a second, third and fourth bulb, and in our model each one keeps glowing as brightly as the first. But the battery has to push out more and more current to keep them all lit, and that has a cost.
• Watch Try it What If? Lab What if you turned the heating down a little? A warm house leaks heat faster than a cooler one. In our model, turning the thermostat from 20 °C to 18 °C on a 0 °C day cuts the heat the house needs by a tenth, from about 86 to about 78 kilowatt-hours a day. On a mild day, the same two degrees save an even bigger share.
• Watch What If? Lab What if your house made its own power? An average American home used about 900 kilowatt-hours of electricity a month in 2022. Some homes make part of it themselves with solar panels on the roof, store some in a battery for the evening, and use a heat pump to warm the house. Follow each idea to see what it could do, and what it can't.