🇺🇸 영어 원문
You’re walking the dog at night, and your little flashlight, which has been getting dimmer, conks out. Instead of stumbling home in the dark, wouldn’t it be great if you could somehow eke a little more energy out of the batteries inside?
That’s not as crazy as it sounds. When a battery-powered device stops working, we say the battery is dead, but it’s not really. It still contains chemical energy, and the voltage isn’t zero; it’s just not high enough to run a current through the light bulb or LED, or whatever load you have.
But with a little physics chicanery, you can indeed get that light to run longer. Much longer! A simple electrical circuit, pairing a transformer and a transistor, can tap that residual energy. It is waggishly called a joule thief circuit.
It’s not only fun to build and kind of mind-blowing, it’s also a great illustration of Faraday’s law of induction, the same principle used in electric generators and induction cooking stoves.
Start with a very simple circuit: a 1.5-volt AA battery connected to a small incandescent light bulb using a single copper wire. It’s a complete circuit. Electric current comes out one end of the battery, runs through a bulb with a tungsten filament inside, and then returns to the other end of the battery. Because that filament is super thin, the current heats it up to a very high temperature, so that it glows white-hot. Luckily, tungsten has the highest melting point of any pure metal.
As long as the circuit is complete, current will continue to flow, gradually using up the battery’s chemical potential energy. As the voltage drops, it produces less current. At some point, there won’t be enough to produce any light.
In a way, this simple circuit can also act like a joule thief. If you leave the switch on, current can continue to flow even after the light goes out, and it will use up the battery’s remaining energy. But who cares about a joule thief that drains a battery and doesn’t produce light?
Today, most devices use LEDs instead of incandescent bulbs. An LED doesn’t produce light by making things hot; instead, it is a solid-state device with an energy gap. When electrons in the current fall to a lower energy level, they release the extra energy as light. It’s much more efficient, because you don’t have all that wasted thermal energy. The only downside is that a white LED often requires about 3 volts, so we need two AA batteries.
As the batteries run down, they eventually drop below the 3-volt threshold. You might still have 2.8 volts, but you get zero light. This is where the magic of the joule thief comes in. The circuit can boost the low voltage and squeeze useful energy from cells that seem dead.
🇰🇷 한국어 요약
배터리가 “다 됐다”고 느껴도 실제로는 전기 에너지가 완전히 사라진 것은 아닙니다. 전압이 장치에 필요한 최소치보다 낮아져서 빛이 안 나는 것뿐이죠. 이 글은 작은 회로인 ‘줄스 티어(joule thief)’를 활용해 거의 죽은 배터리에서 남은 에너지를 빼내 LED를 더 오래 빛나게 하는 원리를 쉽게 설명합니다. 줄스 티어는 트랜지스터와 코일, 즉 변압기 역할을 하는 부품으로 만들어집니다. 이 회로는 전자가 빠르게 켜졌다 꺼졌다 반복하면서 낮은 전압을 높은 전압으로 끌어올리는 방식을 사용합니다. 이 원리는 패러데이 유도 법칙과 연결되며, 발전기나 인덕션 쿡탑과 같은 전기-자기 유도 현상을 이해하는 데 좋은 예시가 됩니다. 청소년들에게는 전기, 전압, 전류, 에너지 변환, 그리고 “실패로 보이는 상황에서 남은 에너지를 재사용한다”는 아이디어를 배우게 하는 유익한 과학 콘텐츠입니다.
🔑 핵심 단어 (Vocabulary)
- battery – 배터리 – A battery still contains chemical energy even when a device stops working.
- voltage – 전압 – The voltage may be too low to run an LED, even if the battery is not completely empty.
- current – 전류 – Electric current flows through a bulb and heats the tungsten filament until it glows.
- circuit – 회로 – A simple circuit can be made with a battery, a bulb, and a copper wire.
- LED – 발광 다이오드 – An LED produces light when electrons drop to a lower energy level.
- energy – 에너지 – The joule thief circuit helps extract useful energy from weak batteries.
- Faraday’s law – 패러데이 법칙 – Faraday’s law of induction is the same principle used in electric generators.
- transistor – 트랜지스터 – A transistor helps control the flow of electricity in the joule thief circuit.
- residual – 남은, 잔여의 – The circuit taps residual energy that remains in seemingly depleted power cells.
- efficient – 효율적인 – LEDs are efficient because they do not waste much energy as heat.
🔗 원문 링크
https://www.wired.com/story/squeeze-more-juice-out-of-a-dead-battery/