Name: 為什麼畫答案卡一定要用 HB 鉛筆？ Why Do I Have to Use a Number 2 Pencil?
Uploaded: 2025-05-11T21:01:10.000Z
Duration: 2 min 36 s

to 不定詞

You probably know the drill: You're handed an exam, and you're told you need to fill out the bubbles completely,

你可能很熟悉這個情況：你拿到考試卷，有人告訴你需要完全塗滿答案格，

過去簡單式

and then reminded that -- for reasons that no one ever explains

並被提醒...而且也沒有告訴你為什麼

情態助動詞 A2

Now, unless you're an artist, you've probably never even seen a pencil that's not number 2,

現在，除非你是個藝術家，你可能從來都沒有看過 2 號以外的鉛筆，

also known as an HB pencil outside the U.S.

2 號鉛筆在美國以外的國家稱作 HB 鉛筆。

The thing is, if you used any other kind of pencil when you took an automatically-scored test,

其實，如果你在考電腦閱卷的考試時，使用其他類型的鉛筆，

However there are reasons that test instructors still tell you to stick to number 2.

然而，考試仍然規定你只能使用 2 號鉛筆是有原因的。

And they have a lot to do with how machines score your tests --

因為這跟電腦閱卷機器的閱卷方式有關──

In 1931, a high school physics teacher named Reynold Johnson was grading exams

在 1931 年，一個名叫 Reynold Johnson 的高中物理老師在改考卷，

when he wondered if there might be a way to score them without actually having to go through every single answer by hand.

他開始思考是否有別的辦法可以不用親自閱卷就能打分數。

He knew that graphite, the writing material in pencils, was electrically conductive.

他知道鉛筆書寫的原料「石墨」可以導電。

and its outer electrons are relatively free to move around within the material.

且其外層電子可以相對自由地在物質裡流動。

So Johnson devised a machine with many small electrical circuits that would pass over an answer sheet.

所以 Johnson 發明了一台裡面有許多小電路的機器，可以審閱答案卷。

If there was a pencil mark on the sheet, it would conduct electricity through one of the circuits,

如果答案欄上有鉛筆畫記痕跡，將會透過其中一個電路導電，

and the machine could record it as an answer.

而後機器可以將其記錄為答案。

Eventually, he sold the idea to IBM, which produced the first mark-sensing machine.

最後，他把點子賣給了 IBM，製造出第一個能偵測鉛筆畫記的機器。

But the number 2 thing didn't become an issue until the next generation of machines were introduced in the 1960s and 70s.

但是 2 號鉛筆直到第二代機器在 1960 到1970 年代被發明後才受到重視。

Those machines had light-sensing devices called phototubes,

那些機器裡有叫做光電管的光感測設備，

and if they did not detect light in a certain spot, they recorded it as an answer.

如果在某個點沒有偵測到光，它就會被記錄為答案。

That made graphite especially useful, because it's better at blocking light than many inks.

這使得石墨特別有用，因為它阻斷光的效果比其他油墨更好。

Graphite reflects most light -- that's why pencil marks are so shiny -- and absorbs the rest,

石墨反射了大多數的光，並且吸收其他的光，這就是鉛筆痕跡如此閃亮的因素，

But for a long time, these optical mark-sensing machines were very picky.

但有很長一段時間，這些光學標記感應機器是很挑剔的。

And that's where the different grades of pencil came in.

而這也正是不同硬度鉛筆出場的原因。

The graphite in pencils is held together by clay, so manufacturers can control how soft or hard it is, and also how dark it is.

鉛筆的石墨是由黏土結合在一起，因此製造商可以控制軟硬及深淺程度。

The softer the graphite, the darker the pencil's mark.

鉛筆具有相應的深淺程度標記。

In the United States, those labels are numbers.

在美國，那些標記用數字表示。

International manufacturers use a different system, with HB corresponding to number 2.

國際製造商使用不同的系統，就像 HB 就等於 2 號。

Number 2 pencils make marks that are just dark enough to be sensed by the machine,

2 號鉛筆讓畫記夠黑，足以被機器偵測，

but also light enough to be erased without leaving a readable mark.

但也能輕鬆地被擦掉，不留下會被偵測到的殘留痕跡。

These days, scoring machines use much more advanced sensors that can detect almost any sort of marks you make,

近來，閱卷機器使用更先進的感應器，幾乎可以檢測所有形式的畫記，

So you could probably take your next exam with any kind of pencil you wanted.

所以下次考試你可以試著用任何一種你想用的鉛筆來作答。

But your SATs probably aren't the time to test that hypothesis.

但是，你的 SAT 測驗可能不是驗證這個假設的好時機。

Maybe bring a couple of number 2s just to be safe.

或許可以帶一些 2 號鉛筆以防萬一。

Thanks for asking, and thanks especially to all of our supporters on Patreon, where,

感謝發問，並特別感謝所有 Patreon 的支持者，

if you support us at four dollars per month or more,

如果你願意用一個月四塊錢來支持我們，

you can submit your questions to be answered right here on SciShow Quick Questions.

你可以傳給我們你的問題，並由 SciShow Quick Questions 幫你解答。

And if you want to keep getting smarter with us, don't forget to go to youtube.com/scishow, and subscribe.

如果你想要和我們一起變聰明，別忘了訂閱 youtube.com/scishow。

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為什麼畫答案卡一定要用 HB 鉛筆？ Why Do I Have to Use a Number 2 Pencil?

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