How to charge the mobile phone without power?

When I was in middle school, I heard the teacher tell such a joke: "A man has a gold tooth on his left and a silver tooth on his right, and his mouth is full of gold and silver, which makes him have a headache." "Why?" "Primary battery reaction!"

There was a video on the internet before, which said, "How can I charge my mobile phone when it is dead?" Of course, if there is no electricity at all, it is impossible to charge. "No electricity" here means that you can create your own electricity without ready-made electricity. In the video, electricity is generated by "galvanic cell reaction".

The concept of primary battery is very extensive, and all devices that convert chemical energy into electrical energy can be called primary batteries. Why is it called original battery? When I first heard someone mention this concept, I wondered if it was called "round" battery, because all batteries are "round". In fact, the English name of the Primary battery is "Primary Cell", in which "primary" means "primary" and can be understood as "basic". After a lot of improvement and development, the current batteries are no longer "basic", but when discussing the principles of these batteries, they will still be called primary batteries, so as long as they can convert chemical energy into electrical energy, they can all be called "primary batteries". There is an English phrase called "primary cell culture", which looks very similar to the English version of primary battery, but they have nothing to do with the meaning. This word actually refers to "primary cell culture", and "cell" refers to both "cell" and "battery cell".

? The reaction in the galvanic cell, the so-called galvanic cell reaction, is usually a "redox reaction". It is generally called "galvanic cell reaction" in English. Of course, galvanic cell can also refer to galvanic cell here. The battery has a positive electrode and a negative electrode. It is the negative electrode that carries out the oxidation reaction, and the electrons of the negative electrode are "deprived", while the positive electrode that carries out the reduction reaction gains electrons. When a battery gains electrons and loses them, it will form different "potential differences". You can think of electrons as water. On the one hand, you get a lot of water, on the other hand, you lose a lot of water. The water level is low. At this time, if the positive and negative electrodes are connected into a "pipe" by wires, electrons will flow from high to low, forming a current in the wires. So in fact, electrons run from the negative electrode to the positive electrode, thus forming a current and generating electric energy. However, due to the negative charge of electrons, according to the standard of "the direction of positive charge movement is the direction of current" in electricity, the direction of current is just opposite to the direction of electron movement, from positive electrode to negative electrode.

? The basic composition of a primary battery: firstly, two conductive electrodes are inserted into the battery, and the water in the battery is called electrolyte solution. Then the ends of the two electrodes that are not in the solution are connected by wires to form a closed loop consisting of electrolyte solution, electrodes and wires. These two electrodes also have a "threshold". It is relatively simple to use two different materials, at least one of which can react with a certain component in the electrolyte solution. The electrode with strong reaction ability connected with the wire will gain the initiative to control the gain and loss of electrons, control the movement of electrons in the wire, and "drive" another electrode with weak reaction ability or no reaction, forming a situation of "gaining electrons" and "losing electrons". But if the two electrodes are made of the same material, there will be a situation that "no one can move anyone", so the two sides are deadlocked and the electrons cannot move in the wire.

? The common simple galvanic cell structure is to insert two kinds of metal sheets (such as zinc and copper) with different "activities" into the acid solution, and one of the metals should be able to react with the acid. These two pieces of metal become the positive and negative electrodes of the battery. But there is no closed loop yet, and when you use this battery, for example, connect the light bulb to the positive electrode and the negative electrode with wires, a closed loop will be formed, and the light bulb may light up. Of course, if you connect the big light bulb of the square street lamp, you may not be able to light it, because this simple battery can't make such a large power output.

? Someone used this principle to make a fruit battery: insert screws made of different metal materials into lemons and then connect them with wires. I heard that some people used one-dollar coins (metal nickel) and five-cent coins (metal copper) to make batteries with salt water or vinegar, but this is an illegal act of "blaspheming RMB", so don't imitate it. Don't take the joke at the beginning seriously. Gold and silver hardly react in oral saliva. Even if the alloy composition inside is active, the current formed is extremely weak, and there will be no feeling of "brain burning".

With the development of batteries, real batteries are certainly not limited to the "simple situation" mentioned above. For example, the two poles of a battery can be made of the same material, and the electrode itself does not participate in the reaction. The "dry battery" used in daily life is called "dry" because the ordinary battery that appeared earlier than it is "wet", and the dry battery does not need to use liquid electrolyte, which is much more convenient to use.

? At present, all kinds of batteries used in mobile phones, computers, electric bicycles and electric cars work by using the basic principle of primary battery reaction, but these chemical reactions are "reversible" and can be "reversed" during charging.

? Although we can use salt, vinegar, fruit, screws and other self-made primary batteries to generate electricity, this way does not generate much electricity and the efficiency is not high. If you want to generate electricity by yourself, a better way is actually to use the principle of "electromagnetic induction".

? Faraday's law of electromagnetic induction says: "When a part of the conductor of a closed circuit cuts the magnetic induction line in a magnetic field, a current will be generated in the conductor, which is called induced current." Our daily use of electricity, whether through hydropower, thermal power, wind power or nuclear power, is based on the principle of electromagnetic induction. Therefore, if you want to make your own power generation equipment, this principle is the most cost-effective: find a strong magnet, let the coil rotate in the magnetic field, and constantly "cut the magnetic induction line" to generate electricity. Now there are also "hand-cranked generators" on the market, which can be bought for exercise, but if you want to save electricity, forget it. After all, the power is far from enough for most household appliances. Self-generating fun running lights, hand-held self-generating flashlights and other small toys that allow people to generate electricity manually also use the principle of electromagnetic induction, that is, the relative movement of coils and permanent magnets generates current.

? "Friction electrification" is an "electrical enlightenment course" that I have learned in primary school science class. Rub glass rods with silk, or rubber rods with fur. After rubbing, you will find that they have the characteristics of attracting light and small objects (paper). The process of triboelectrification is actually the process of electrons transferring from one object to another. Generally, there will be charge transfer when two objects are rubbed together, but many times the transferred electrons will run away immediately, so the phenomenon is not obvious. The "static electricity" in life is generally generated by friction, and the voltage is usually high, but because of the small amount of electricity, it will basically not cause harm to people.

Although "friction electrification" is very common, the electricity generated is very small, so it is difficult for us to generate electricity in this way. It is likely that the electricity generated is not much, but it is realized on the spot. But at present, some scientists are studying and making some special materials to make friction power generation generate more electricity. It is predicted that in the future, all the electricity generated by people's friction during walking and sports can be used to power our low-power wearable devices.

? If you really want to generate electricity by yourself, you can consider the "electromagnetic induction" method first. Be a fruit battery if you are afraid of being tired. But personally, I think it's a waste not to eat such good fruit.