Film: 1217

Science | 1940 | Sound | B/W

Synopsis:

Magnetism explained - 1940's
A boy and a girl are playing with a home made telegraph. The girl is outside sitting at a table watching the machine clicking. Whilst the boy makes it work from afar. He explains to her about the magnet as he comes nearer winding up the wire and now they are going to experiment with magnets inside the workshop. He shows her his magnet collection. She is asking about N and S and he explains about the magnetic pull of the North Pole and how a compass works. She discovers how two magnets have ends that repel and ends that contract. They have a whole array of things on the table, nails, iron powder, pencils, rubber etc. She discovers how magnet affects certain things on the table. The boy shows her how a nail can become temporarily magnetized and attract other nails. The boy shows how to form a magnet by rubbing a piece of steel on a magnet. Now they put a large piece of glass raised from the table, so they can put magnets underneath and create the shape of a force field above the glass with iron filings, as they arrange themselves in two round shapes above magnet leads. A picture of the earth as a magnet. The girl asks about the telegraph. The boy shows her how electromagnetism works by winding a wire around a piece of steel and connecting it to a battery with a switch. An iron bar at the other end of the wire becomes magnetized when the switch is on and stops when its off. A diagram explains how a telegraph works then we see the clicking being made. The girl is excited, now she wants to know about a telephone. The boy wants to show her how an electric motor works. A diagram explains the switching of the magnetic heads from north to south. Which causes spinning. The girl realizes the importance of magnets and now the boy is going to show her how to form electricity with magnets, using the same electric motor. Measuring the power that comes the other end through the wire by putting a light bulb that shines.
A summary of all that has gone on with a voiceover. A picture of a giant dynamo compass, a train coming, crossing under pillars.


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