Small production: electromagnetic train
Small production: electromagnetic train
Another combination of copper wire, battery and strong magnet

another way to combine copper wire, battery and strong magnet: they can be turned into an electromagnetic "small train".

the body of the train is a battery with strong magnets on both sides, and the track is a solenoid wound with bare copper wire. When the "small train" is put into the copper wire, the magnets at both ends of the battery come into contact with the copper wire, forming a closed loop locally, and the electrified solenoid generates a magnetic field and interacts with the magnet, providing the small train with power to move forward.

in the video I use bare copper wire with a diameter of 1mm, winding a coil around a pen. Note that the enamelled copper wire is not suitable for this experiment because there is insulation outside and it is troublesome to scrape it off. Ensure that copper coil diameter> magnet diameter> battery diameter. If you want to get a long "track", you need to prepare enough copper wire.

the direction of the magnets on both sides of the battery is also very important to get the "little train" moving. As mentioned in the video, you need to find the two mutually exclusive stages of the magnet, and then clip the battery between the two mutually exclusive stages. In other words, both the NS battery SN and the SN battery NS can be connected, but if the NS battery NS is connected, the battery cannot move in the copper wire, and the force on both sides of the magnet is offset.

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the influence of magnet direction can be illustrated by the following diagram:

(picture source: PhysicsGirl)

when the circuit is connected, the intensity of the magnetic field generated by the copper tube is symmetrical around the center of the battery, and the intensity is weaker on the outside. The force on the inside end of the left and right magnets should be the same, and the direction depends on the direction in which the magnet is placed (the same is true of the outer end). If the magnet is placed like this in the picture, there will be two larger forces to the right and two smaller forces to the left, resulting in an imbalance of force, which can push the battery to the right; and if it becomes the connection of the NS battery NS, the force will become a big and a small force to the left and right, and the final force balance.

this kind of strong magnet is not easy to tell which is the N pole and which is the S pole, so after finding the mutually exclusive poles, we are still not sure which direction the "little train" will go. The solution is simple: just shove the small train into a copper pipe and try it. If it retreats itself as soon as it is pushed in, it can move forward as long as it is put in through the opening on the other side of the coil or the battery is turned over.

my "little train" runs to the end quickly every time because of its short track, so it doesn't feel the obvious battery heat. However, you should still pay attention to the heating problem of the battery, especially when it is stuck in the copper coil, take it out as soon as possible. This could have been connected into a ring and let it run in a circle, but the coil I bought 15 meters of copper wire is not long enough, so I didn't try it (although the copper wire is cheap, but I don't want to buy any more. ). If replaced with a smaller diameter of the No. 7 battery, it would save more copper wire.

PS: the original idea of this game should come from tubing blogger Jun AmazingScience, whose video tutorials are also very detailed. If you have conditions, you can follow them.