圣诞彩灯是串联电路还是并联电路?
Are Christmas Lights in Series or Parallel?
1733字
2020-01-02 18:31
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火星译客

Why don't your Christmas lights work? Sadly, in the event of a string of lights going out on your tree, replacing the strand is usually the best option. It's pretty difficult to find that one bulb that's causing the problem. However, this is a great time to look at the difference between series and parallel circuits.

你的圣诞彩灯怎么不亮了?不幸的是,如果你的圣诞树上有一串灯熄灭了,换掉这串灯通常是最好的选择。很难找出那只引发问题的灯泡。然而,现在正是发现串联与并联电路之间的区别的好时机。

A Simple Circuit

最简单的电路

Just about the simplest circuit you can create uses just one battery and one light bulb. In one fun activity, you can give a person one wire, one battery and one light bulb. Ask the person to make the bulb shine. It's possible to get it to work, but it can still cause some trouble for people.

只用一个电池和一个灯泡你就可以做出最简单的电路。有趣的活动:找一个人,给他一根电线,一个电池和一只灯泡,再请他将灯泡点亮。尽管我们能够让该电路工作起来,但无可避免的是,这会给人们带来一些麻烦。

In order to get the bulb to glow, you need a complete circuit. There has to be a path for the current to come out of one end of the battery, go through the filament in the bulb and then return to the battery. Here's how that could work.

要想点亮灯泡,你需要的是完整的电路。创造一条电路是十分必要的:它可以让电流从电池的一端出来,穿过灯泡的灯丝,然后回到电池。这就是它的工作原理。

A simple circuit with a battery and bulb.

带电池和灯泡的简单电路

Rhett Allain

瑞德·艾蓝

When current passes through the filament, it makes the filament get super hot. Super hot things glow. That's all the bulb does. But why the glass on the outside? That is there to keep air away from the super hot filament. With air in contact with the filament, it would burn out.

当电流通过灯丝时,灯丝的温度会升高到极热状态。而超高温的东西会发光。这就是灯泡的作用。但是为什么要在外面装上玻璃呢?那是为了让空气远离超热的灯丝。当空气与灯丝接触时,灯丝就会烧坏。

If you take away any one of the parts for the complete circuit, there would be no current and no glowing bulb.

如果你把整个电路的任何一个部分拿走,就不会有电流,也不会有发光的灯泡。

Light Bulbs in Series

串联电路中的灯泡

Now you want to connect two light bulbs to battery. Here is one way you could do that.

现在你想把两个灯泡连到电池上。方法如下。

A circuit with two lightbulbs connected in series.

由两个灯泡构成的串联电路。

Rhett Allain

瑞德·艾蓝

In this case, there is just one path for the current to follow. The current that goes through the first bulb also goest through the second bulb. If you remove any part of this circuit (like take out a bulb), everything goes out. If you wanted, you can make a similar circuit with 10 or 20 bulbs. Just connect them all in a line so that the same current goes through each one. This is a series connection.

在这种情况下,只有一条路径供电流通过。通过第一个灯泡的电流也通过第二个灯泡。如果你移开这个电路的任何一部分 (比如取出一个灯泡),所有灯泡都会熄灭。如果你愿意,你可以用10或20个灯泡做一个类似的电路。只要把它们连成一条线,让相同的电流通过各个部分。这就是串联电路。

Light Bulbs in Parallel

并联电路中的灯泡

There is another way to connect two light bulbs. Check it out.

还有另一种方法可以连接两个灯泡。试试看吧。

A circuit with two lightbulbs in parallel.

两个灯泡构成的并联电路。

Rhett Allain

瑞德·艾蓝

The difference in this circuit is that each lightbulb has its own "path" to the battery. If you break one of these bulbs, it doesn't really do anything to the other bulb.

这个电路的不同之处在于,每个灯泡都有自己的 “路径” 连接电池。如果你打碎了其中一个灯泡,它不会对另一个灯泡产生任何影响。

Here is a quick demo showing the difference between bulbs in series and bulbs in parallel.

下面我们将通过快速演示,向您展示串联灯泡和并联灯泡的区别。

Oh, and just like the lightbulbs in series you can do this with many, many bulbs.

哦,就像串联灯泡一样,你可以用很多很多灯泡来完成试验。

Christmas Lights

圣诞灯

Now we can get to the fun stuff. What about the lights you put on your Christmas tree? Are those lightbulbs in series or parallel? What do you think? Here are two hints.

现在我们来看看有趣的东西。那你挂在圣诞树上的灯呢?那些灯泡是串联的还是并联的?你觉得呢?这里有两个提示。

Hint number 1: if you pull out one of the lightbulbs from a strand, the rest of the lights go out. Ok, this isn't always true. Many lights are actually two sets of strands. If you pull out a lightbulb, half the strand goes out.

提示一:如果你从一根线中抽出一个灯泡,其余的灯就灭了。好吧,这套理论并不总是对的。很多情况下,光亮其实来自两股电流。如果你拉出一个灯泡,其中一半的路线所联结的灯泡就会熄灭。

Rhett Allain

瑞德·艾蓝

Here you can see that this strand has one bulb removed and non of the other lights are on (even though the power is on).

在这里你可以看到,从这条线路线取出一只灯泡,其他的灯也熄灭了 ( 即使电源是开着的 ) 。

Hint number 2: In some cases, one of the lightbulbs in a strand may "burn out". When a lightbulb burns out, typically it will be due to a broken (or melted filament). In this case, the strand would look like this.

提示2:在某些情况下,串联电路中的灯泡可能会被 “ 烧坏 ”。当灯泡烧坏时,通常是由于灯丝断了(或熔化了)。在这种情况下,电路是这样的。

Rhett Allain

瑞德·艾蓝

Notice the one bulb is indeed out but the other bulbs are on. But is the filament actually broken? Yes, if you look closely, you can see something like this.

注意,确实有一个灯泡坏了,但其他灯泡是亮着的。但是灯丝真的断了吗?是的,如果你仔细看,你会看到类似的情况。

A broken filament in a Christmas light.

圣诞灯丝断了。

Rhett Allain

瑞德·艾蓝

Ok, now what's the answer? Are the bulbs in series or parallel? Based on hint 1, it seems the lights are in series. Based on hint 2, it seems they are in parallel. The answer is that the lights are in series. Yup.

好的,那现在得出的答案是什么呢?灯泡是串联的还是并联的?根据提示1,看起来灯是串联的。根据提示2,它们似乎是并联的。答案是灯是串联的。是的。

But how can this be? How can you have one light with a broken filament and still have the other lights on? In the physics world, we call this "the magic of Christmas". Ok, not really. The answer is that the lights are connected in series but the bulbs have a trick.

但这是怎么回事呢?怎么可能一只灯泡的灯丝断了,而另一只灯还亮着?在物理学界,我们称之为 “ 圣诞魔法 ” 。好吧,这只是幻想。答案是这些灯是串联的,但是灯泡之所以发亮是因为有个小窍门。

Let's take a closer look at one of the light bulbs in the strand.

让我们选取该线路中的其中一个灯泡仔细研究下。

A shunt wire (bypass wire) in a Christmas light.

圣诞灯中的一根分路电线 ( 旁路电线 ) 。

Rhett Allain

瑞德·艾蓝

This is a view of a broken bulb. At the end of the metal posts you can see the broken filament - so this is a burned out bulb (plus I broke the glass so you could see better). But what about that metal wire wrapped around the posts (indicated with the red arrow)? What is that for? If it was just a normal wire, this would short out the bulb. It would mean that most of the current going through this bulb would run through this wire and not through the filament. With very little current, the filament would not glow.

这是一个坏掉的灯泡。在金属杆的末端,你可以看到灯丝是烧断的——所以这是一个烧坏的灯泡 ( 加上我打碎了玻璃,所以你可以看得更清楚 ) 。但是绕在柱子上的金属丝(用红色箭头表示)呢?那是做什么用的?如果只是一根普通的电线,灯泡就会短路。这意味着大部分通过灯泡的电流会通过导线而不是灯丝。如果电流很小,灯丝就不会发光。

So, in order for this bulb to function properly in a strand (with a good filament), there shouldn't be a current going through this bypass wire. Ok, now let me make some guesses as to how this magic Christmas light works. Yes, I could ues the internet to find out more about this bulb, but I really like guessing.

所以,为了让这个灯泡在同一线路中正常工作 ( 用一个好的灯丝 ) ,电流是不允许通过该旁路导线的。好了,现在让我来猜测一下这个神奇的圣诞灯是如何工作的。是的,尽管我可以上网找到更多相关信息,但我真的很喜欢猜测。

  • Like I said, in a functioning bulb this wire does not conduct electrical current. There must be some type of insulator between the bypass wire and the filament post.
  • When the filament burns out, all the current going through all the bulbs in series stops.
  • Without current going through the bulbs, there is a high potential difference between the bypass wire and one of the filament posts (I will show why below). This high voltage (120 volts) across a very short distance produces a very high electric field.
  • If the electric field is high enough, it could cause and electric breakdown in the material and turn it from an insulator into a conductor.
  • Boom. The rest of the lights work now (but it probably doesn't make a boom sound).
  • 就像我说的,要使灯泡正常工作,这条电线得是不导电的。在旁路导线和灯丝柱之间必须有某种绝缘体。
  • 一旦灯丝烧坏,所有通过灯泡的电流就会停止。
  • 在没有电流通过灯泡的情况下,旁路导线和灯丝灯柱之间存在很大的电位差 (我将在下面说明原因)。这种高压 ( 120伏特 ) 在很短的距离内将产生很高的电场。
  • 如果电场足够大,就会引起材料的电击穿,使其从绝缘体变成导体。
  • “ 砰 ”。其余的灯现在可以工作了 ( 但可能不会发出轰隆声 ) 。

But how does a broken filament make a high voltage right at the bulb that is broken? Let's pretend like we have a different circuit. In this one, I have 5 lightbulbs in series connected to a battery. Oh, and all the lightbulbs work.

但是一个断丝是如何在断丝的灯泡上产生高压的呢?假设我们有一个不同的电路。在这个例子中,我有5个灯泡串联在一块电池上。噢,所有的灯泡都能工作。

Resistors in series

串联电路中的电阻

Rhett Allain

瑞德·艾蓝

Suppose each lightbulb has a resistance R (it doesn't matter than lightbulbs are non-ohmic). If I have a 10 volt battery connected to them, then the total change in electric potential around the loop must be zero volts. Also, since the bulbs are in series, they have to have the same electric current (I). This means that I can write:

假设每个灯泡都有一个电阻R ( 这与灯泡的非欧姆无关 ) 。如果我有一个10伏的电池,那么回路周围的总电势变化一定是0伏。此外,由于灯泡是串联的,它们必须有相同的电流 (I),这意味着我可以做这样的运算:

La te xi t 1

So each bulb has a 2 volt electric potential across it. But now let's say one of those bulbs break. With an open circuit, there is no longer a current. Here is the new diagram.

所以每个灯泡都有2伏的电势。现在假设其中一个灯泡坏了。在开路的情况下,就不再有电流。这是新的图表。

Resistors in series with a break in the circuit.

电阻与电路中的断路串联。

Rhett Allain

瑞德·艾蓝

Even though there is a break, the change in electric potential around this loop still has to be zero volts. But since there is no electric current, the change in potential across each resistor is zero. This means that the full 10 volts must be across the gap. This 10 volt gap potential creates a large electric field that breaks down the insulator. That's the magic of the Christmas lights.

即使存在断路,这个回路周围的电势变化仍然是零伏特。但是因为没有电流,所以每个电阻之间的电势变化为零。这意味着10伏特的电压必须穿过这个间隙。而这个10伏特的间隙电势会产生一个巨大的电场,击穿绝缘体。这就是圣诞彩灯的魔力。

My Lights Still Don't Work.

我的灯泡还是不亮。

These lightbulbs have this awesome bypass wire inside the bulbs. However, if the light bulb is not even plugged in even the bypass wire won't work. So, if you have a strand that doesn't work here are some things you can try.

这些灯泡内部有一根强大的旁路电线。然而,如果灯泡没有插上电源,即使是旁路电线也不会工作。所以,如果你手边的电线不工作,你可以猜想下其他可能的原因。

1. Is it plugged in? Yes, you should check this. A strand of lights that isn't plugged in won't work. If you have lights plugged in outside and they get wet, they will likely trip your Ground Fault Interrupter (GFI). You have these on the outlets in your bathroom (with the test and reset button). When the circuit gets wet it can trip this.

1. 插上电源了吗?是的,你应该检查一下这一点。一串灯泡不插电的话确实不会亮。如果你的电灯插在外面,它们被弄湿了,它们很可能会阻断接地故障断续器(GFI)的正常工作。你的浴室里的插座应该会带有该装置 ( 带有测试和重置按钮 ) 。当电路遇水时,断续器也就不工作了。

2. Check the fuse. I'll assume that you checked your household circuit breaker. If that was tripped, you could probably tell because of the other things that weren't working. But there are also fuses in the little plug on the end of the strand. There is a sliding door and it looks like this.

2. 检查保险丝。我想你已经检查过家里的断路器了。如果不是这方面的问题,你可能会说,那是由于其他。但是在链的末端也有保险丝。有一个滑动门,它是这样的。

Rhett Allain Fuses in a strand of Christmas lights.

瑞德·艾蓝在一束圣诞彩灯的映衬下若隐若现。

If you connect too many strands of lights together then the current will be too large. The fuse will go out to prevent these things from getting too hot. However, sometimes these little fuses just get loose after storing the lights in the off season. It doesn't hurt to check them.

如果你将很多电线连接在一起,那么电流就会太大。保险丝会烧断,以防这些东西的温度过高。然而,有时这些小保险丝只是后才会松动。检查一下也无妨。

3. Look for a loose bulb. If a strand doesn't work and you checked the other stuff, there's a good chance the problem is a loose bulb. It can be quite a challenge to locate a loose bulb. Normally, I just push on each bulb to see if I can get the strand of lights to come on. There is also a special tool you can use. Mine looks like this:

3.寻找一个松动的灯泡。如果一根电线不工作,而你已经核查了其他原因,那么很有可能是灯泡松了。要找一只松动的灯泡是一个相当大的挑战。通常情况下,我只是按下每个灯泡,看看能不能让那串灯亮起来。还有一种特殊的工具可以使用。我所采用的工具是这样的:

A Christmas light detector.

圣诞灯探测器。

Rhett Allain

瑞德·艾蓝

I'm not completely certain, but I think this thing detects small electric currents. If you have a loose bulb, there will be a slight alternating current going to and from the outlet to the break. On the other side of the break there won't be the same current. You can detect a current by detecting the magnetic fields that go along with the current. But now I'm not so sure this is the way these detectors work. I'll have to think about this is a little bit.

尽管我不完全确定,但我想这东西能探测到小电流。如果你的灯泡是松动的,那么从出口到断路会有一股轻微的交流电通过。在断路的另一边就不会产生相同的电流。你可以通过探测随电流变化的磁场来探测电流。但现在我不确定这是不是探测器的工作方式。我需要思考一下。

4. Check for squirrels. Yes. Look at these lights on a tree in my front yard.

4. 检查是否有松鼠。是的。看看我前院树上的这些灯吧(松鼠的杰作)。

A broken strand of Christmas lights.

一串破碎的圣诞彩灯。

Rhett Allain

瑞德·艾蓝

I guess squirrels hate Christmas.

我猜松鼠讨厌圣诞节。

Oh, and just for fun I made a video version of this same thing.

哦,为了好玩,我将这次实验做成了一个视频。

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