4. Anatomy of a flashlight
1) Electric current: The smallest unit of all matter is an atom; an atom consists of neutrons (uncharged) & protons (positive charge), electrons (negative charge). The electrons in a circuit are constantly moving from one atom to the next, and it becomes an electric current. The key device that makes the electrons move is the battery. The chemical substances in the battery are carefully selected through research. The chemical reaction between them can make the excess free electrons gather at the negative end, and at the positive end Become desperate for extra electrons, and bathroom chemistry turns into electricity.
2) The switch has only two states, on or off, and the current can only be present or absent. Light bulbs can also only emit light or not. Like the previous Morse code, the binary code of Braille is the same.
5. Communication around the corner
Question 1: How to communicate when the flashlight is not visible, that is, how to communicate at a long distance?
Method: By means of power supply + wire. Connect the battery, light bulb, switch, and guide to a circuit, then put the switch in your house, and put the light bulb in your friend's house. Cooperate with the code you negotiated, and you can send a message to your friend.
, and then make a light bulb in your house, and he can send you a message when the switch is in his house.
Problem 2: The longer the distance, the longer the wire required, the higher the cost and the higher the resistance, the higher the resistance, the lower the current and the dimmer the bulb.
Method 1: Thick wire, but high cost.
Method 2: Increase the voltage. If the voltage is strong enough and the battery is large enough, the two communication parties only need to ground one end and use a wire at the other end to reduce costs.
6. Telegraph & Relay
1) Telegraph: Take some action on this end of the line to cause some kind of change on the other end of the line. In 1836, Morse used the electromagnetic phenomenon (a magnet is formed by passing an electric current on an iron rod that is wound with hundreds of turns of wire; the more wires, the stronger the resistance, which can prevent the short circuit phenomenon of the earth magnet; disconnection Electric current, iron rods will lose their magnetism) invented the telegraph, and the code for which he was named. The invention of the telegraph marked the beginning of modern communication.
2) The composition of the telegraph machine:
- Transmitter: a switch, tap to move it up and down, generating dot and dash Morse code
- Receiver: A piece of electromagnet pulls a metal rod, the transmitter key is pressed, the electromagnet pulls the metal rod down, releases the key, and bounces back to its original position to receive point and swipe information.
3) The biggest problem with the telegraph is the resistance caused by the long wires.
4) Relay: Solution: Set up a relay system to forward information from the middle. The invented device is a relay. Adding a device similar to the sender at the receiver can synchronize the information of the sender and send it to the next receiver
terminal, and this cycle, amplifies the "signal".
A relay is an excellent device. It is a switch, but it is not switched manually but by means of electrical current. Amazing things can be done with this kind of equipment. In fact, you can assemble most parts of a computer out of relays.