The method is simple as follows: use small light bulbs, very small ones (such as pendants or toy lights, which are sold in hardware stores). Then connect the lamps with two thin enameled wires respectively. The other ends of the two wires are used to connect the positive and negative poles of the battery you want to test. According to the brightness of the small light bulb, the battery charge can be judged.
2. Take a broken umbrella, remove the cloth, take a wire, connect one end to the TV or radio, and the other end to the umbrella, which is a good signal receiver. If you want to be professional, put more threads around the umbrella. This is the cheapest and quickest way, but it's a bit funny.
Put a match and a sewn needle together, wrap them tightly with aluminum foil wrapped in cigarettes, then bend and seal the end of the aluminum foil with a matchstick and tighten it. Then install the directional tail near the tail and pull out the needle, which becomes a very simple recoil rocket.
In the experiment, a small rocket was placed on a wire rack, a match was lit, and the part of the aluminum foil tube covered with a matchstick was heated. When the temperature rises to the ignition point of the matchhead, the matchbox in the foil is ignited, which makes the surrounding air expand rapidly and the gas is ejected from the tail mouth at high speed. Due to the recoil, the rocket launcher flew forward from the frame.
If two matchsticks are put together face to face and wrapped in aluminum foil, both ends are not closed. Put it on the table and heat it from the middle. When the match in the cylinder is lit, the gas is ejected from both ends, and the aluminum foil cylinder remains on the frame, which shows the momentum conservation of the system.
4. Rivet two identical protractors at the center of the circle and rotate flexibly. Cut a gap with a length of 1 cm along the right end of the protractor. When measuring the angle, make its opening coincide with both sides of the angle to be measured, and the scale indicated by the notch is the degree of the angle; When drawing a corner, first aim the notch at a specified proportion, and then draw two rays along the opening. This protractor can also measure the angle of solid objects (such as nuts).
Because this protractor works like scissors, we call it "scissors protractor".
five
I recommend my classmate's small production to you.
He made a small electronic balance model. Note that this model can only weigh very light objects, such as two small pieces of paper. The materials needed for production are: a wooden board (preferably thinner, not too big), a washer, a paper clip, an awl, an electric soldering iron, several wires, two light-emitting diodes and a battery. These materials are easy to find. If there is no led, you can go to the electronic market to buy it. They are very cheap.
The manufacturing process is as follows: drill a small hole in the middle of the board with an awl, bend a paper clip into a hook shape and fix it on the board through the small hole perpendicular to the board, as long as the washer can be hung on the hook. Then take two paper clips and straighten them in half, leaving only one corner. In fact, the straight part is the arm of the balance, and the remaining curved part is the tray. Another paper clip does the same thing. Then use the middle washer to weld the two paper clips together, and the paper clips should be in a straight line. Then hang the washer on the hook, adjust the distance between the hook and the board, about 3 mm, then fix two paper clips under the two trays, and prepare led as the indicator light next to the paper clips. A circuit is arranged under the board, and the balance is equivalent to a single-pole double-throw switch. This circuit is equivalent to two loops, using a power supply and two light emitting diodes. As long as the left side sinks, the tray on the left side will be connected with the pin below him, so that the circuit will be connected and the diode will emit light; If the two sides are equal in weight, the circuit is blocked and both diodes are not lit.
Add some hope you can be satisfied!
Finally, I wish you a smooth delivery and a happy mood.