Placeholder Image

字幕列表 影片播放

  • I'm playing with a compass needle near wire and it was discovered by Hans Christian thirsted in 18 20 that if you have a direct current passing through a wire and I got one here that goes down under the table, goes under the table and then it goes round in a circuit and I've got Well, I haven't turned it on yet, but it's gonna be 10 volts going through their leading to a current on Earth had discovered in a public experiment that he did in front of a big audience.

  • He found that you could defect the direction of the company.

  • I've got my compass needle, the red points towards herself.

  • The silver sight goes towards the north now going to turn this around the wire and you can see as I do that it still points in the same direction.

  • As soon as I turn on electric current thirsted found that the direction of the needle will move.

  • So there it is, that's pointing north.

  • North is that way, and I'm going to turn it a bit further.

  • So at this stage it's pointing it seems east, but that's actually north.

  • And now I'm going to go to the voltage supply and put 10 AM through this war and you can see is you turn that on the compass needle no longer points east.

  • It points more towards this direction and I'll turn it off and I'll turn it on and you can see that it ends up being deflected.

  • Now you can think of this as being a magnetic field this way on the magnetic field, pointing that way.

  • Some of these two magnetic fields I can represent by saying that's the Earth's magnetic field on this is a much bigger magnetic field at right angles to it because I turn this round by 90 degrees on that points in this direction.

  • So the Compass Needle tells me the direction of this resultant magnetic field of some of these two, and it gives a direction.

  • And now, if I turn this round another 90 degrees, so I probably got it lined up exactly right.

  • But now I've got a magnetic field given by the green pointing that way on a magnetic field, roughly pointing in the opposite direction, and this is smaller than the magnetic field due to the current.

  • So I get a little magnetic field pointing that way.

  • So it's pointing in the opposite direction.

  • Now, if I move it around a bit further, you can see the direction change.

  • And then when I go away around back to the starting point, magnetic field seems to have turned around, curled around and come back into the same direction.

  • So what first had discovered was the magnetic field near the wire circulates around the white as though it's going in a circular path.

  • It's bigger, close in, and it's weaker.

  • Further out.

  • There is a relationship by somebody else called Impair, which relates what happens as you measure the magnetic field around here times the distance and that's related to the current in the wire.

  • We have a rule.

  • If the current is flowing upwards, you point your thumb in that direction, and then your fingers curl around the wire on.

  • That tells you the direction of the magnetic field.

  • So there's something called the right hand rule to tell you the direction of this sink.

  • So you're seeing the first example through this experiment of how a compass needle is moved by current.

  • Now you from that you can build a way of sending messages down wires.

  • You start off with the current, which will then deflect a needle one way, and then it goes back to where it waas deflected on.

  • This is the beginning of calligraphy, sending electrical messages down wires, dots and dashes if you like.

  • And then you contend information somewhere else.

  • If you ever seen the movie The General with Buster Keaton from Way Back, it's meant to be in the Civil War period, which is, I don't know, mid 19th century on, they had telegraph wires alongside the railroad's on the way you could set information was through these telegraph wires down to let people know what the Army was up to.

  • So Buster Keaton spent his time pulling down all the telegraph wires to make sure that the messages couldn't get through somebody doing Morse code dot dash.

  • Well, in this case, it's going on or off, and I could do dot and then I have to wait and dot And then there's a wait and then another dot and then I could have a dash, which would be longer, so we have it on there for a longer period, and then off.

  • I'm making this up as I go along.

  • This is the beginning of sending messages is the turning point inside is more of a turning point in science because this is an electric current passing down a wire, producing a magnetic effect.

  • So with this discovery, bursted had discovered a connection between electricity and magnetism.

  • They weren't separate subjects after this.

  • They were part of the same subject which we now called electromagnetism.

  • You know what?

  • Today I'm gonna go to the left.

  • Not right.

  • I don't see why I always curls the same way.

  • That's the way nature is.

  • What can I tell you?

I'm playing with a compass needle near wire and it was discovered by Hans Christian thirsted in 18 20 that if you have a direct current passing through a wire and I got one here that goes down under the table, goes under the table and then it goes round in a circuit and I've got Well, I haven't turned it on yet, but it's gonna be 10 volts going through their leading to a current on Earth had discovered in a public experiment that he did in front of a big audience.

字幕與單字

影片操作 你可以在這邊進行「影片」的調整,以及「字幕」的顯示

B1 中級

右手規則--60個符號 (Right-Hand Rule - Sixty Symbols)

  • 0 0
    林宜悉 發佈於 2021 年 01 月 14 日
影片單字