在不知道歐姆法律的情況下，很難進入電子產品。以[georg obm]命名它描述了線性電路中的電流和電壓關係。但是，有兩種法律更加基本，俄亥俄州的法律差不多尊重。那些是基爾霍夫的法律。
在簡單的條件下，Kirchhoff的法律真的表達了能量保護。 Kirchhoff的當前法律（KCL）表示，進入單點（節點）的目前必須具有完全相同的電流。如果您更加數學，可以說，進入的當前和流出的總和始終為零，因為與當前進入的電流相比，電流將具有負符號。
你知道串聯電路中的電流始終相同，對右？例如，在具有電池的電路中，LED和電阻器，LED和電阻器將具有相同的電流。那是kcl。電流進入電阻器更好地與當前流出並進入LED相同。
當有多個以上的電線進入一點時，這大多是有趣的。例如，如果電池驅動3個神奇相同的燈泡，則每個燈泡將獲得總電流的三分之一。電池電量的導線與3個燈泡連接的節點是節點。目前的所有進入，必須等於所有目前出門。即使燈泡不相同，總計仍然是平等的。因此，如果您知道任意三個值，則可以計算第四個值。
如果您自己自己玩，可以模擬下面的電路。
來自電池的電流必須等於電流進入電池的電流。左側的兩個電阻器，最佳通過它們（1.56 mA）。在模擬器的捨入錯誤中，拆分的每個分支都有其總數（注意底部腿具有3k總阻力，因此較少電流）。
Kirchhoff的電壓法（KVL）表示環繞循環的電壓必須總和為零。佔據一個簡單的例子。 12V電池在其中有一個12V燈泡。燈泡穿過多少電壓？ 12V。如果有兩個相同的燈泡，它們仍將在每個燈泡上看到12V。
您可以模擬此電路以查看效果。帶有兩個燈泡的循環在其中12V，每個燈泡都有一半，因為它們是相同的。右側路徑具有不同的電壓，但仍然必須增加12個。
所有本身，KVL都不會非常有用，但是有一個原則稱為疊加。這是一種奇特的說法，你可以將復雜的電路打破成碎片並看看每件作品，然後加回結果並獲得最佳答案。
分析
您可以使用這兩種定律來使用節點分析（對於KCL）或KVL的網格分析來分析電路，無論它們是多麼複雜。唯一的問題是您充滿了大量方程，可能必須將它們作為同時方程式解析。幸運的是，計算機真的很擅長，電路分析軟件經常使用這些技術之一來查找答案。
考慮這個電路：
這實際上太容易了，因為我們知道v1和v2最好的門（電池5v和0，因為v2連接到地）。此外，人類會知道計算相當於R2和R3，但在更複雜的電路中可能並不明顯，尤其是計算機。
標記為Vx的節點具有三個電流。 I1是電池的電流和R1流入。I2是流過R2的電流，I3是流過R3的電流。您可以輕鬆地為所有三種電流編寫方程式：
I1 =（vx-v1）/ r1
I2 =（vx-v2）/ r2
I3 =（vx-v2）/ r3
當然，除了VX之外，我們知道所有東西的價值觀，所以：
I1 =（VX-5）/ 300
I2 = Vx / R2
i3 = vx / r3
請注意，上面的第一行是“向後”，因為I1流入節點Vx，其他情況流出;有幾種方法可以選擇處理這一點。現在使用KCL我們知道：i1 + i2 + i3 = 0您可以替換所有我的等式：
（VX-5）/ 300 + Vx / 500 + Vx / 100 = 0
（5VX + 3VX + 15VX）/ 1500 = 5/300
23VX / 1500 = 5/300
23Vx = 1500（5/300）
Vx = 25/23 = 1.09V（約）
對於上面的第2行，300,500和100的最小常見倍數為1500，我們將5/300添加到兩側以單獨獲取VX術語。在第4行中，我們將兩側乘以1500到達解決方案。
如果您查看模擬，您將看到VX為1.09V。現在，您可以通過插入值來返回等式並獲取I1，I2和I3。當然，真正的問題得到了Thornier，通常用你必須解決的等式系統結束。
如果您真的希望追求更高的數學，您可能會在下面的節點分析上欣賞Khan Academy視頻。請注意，他們明確處理負電流的思想。如果您想在我們的示例上使用它們的數學，那麼I2和I3顯式為負，i1是derived from 5-Vx instead of Vx-5. then you wind up with -23Vx=-25 and get the same result in the end. That’s how math is.
The other way to do this sort of systematic analysis with KCL and KVL is mesh analysis. There you use superposition and simultaneous equations. but don’t worry — it isn’t as hard as it might sound. rather than go into that, you can view another Khan Academy video on the subject. just dust off those algebra skills.
歷史
[Gustav Kirchhoff] was a German physicist who worked all this out in 1845, about 20 years after [Ohm] worked out his law. Actually, [Ohm] wasn’t first, he was just the first to talk about it. [Henry Cavendish] figured out Ohm’s law in 1781 using Leyden jars (big capacitors) and his own body as an ammeter. He’d complete the circuit with his body and judge the current flow by the amount of shock he received. now that’s dedication. [Ohm] had a better experimental setup and — as far as we know — didn’t shock himself as a matter of course.
You might think that [Ohm] was well respected for his discovery, but that wasn’t the case. The establishment was very upset with his findings. One German yearbook of scientific critique labeled it “a web of naked fancies.” The German minister of education called it a “heresy.” It was in opposition to Barlow’s law (suggested in 1825 by [Peter Barlow]) which said that current was related to the diameter of the wire and the length of it.
Actually, [Barlow] wasn’t completely wrong. He used a constant voltage and did not understand (as [Ohm] did) that the voltage source had an internal resistance. [Ohm], in fact, switched from batteries to thermocouples because at the time they had a much more stable output and predictable low internal resistance.
It is hard to imagine today, but there was a lot of experimentation and law writing back then — not all of it correct, obviously. often the person we associate with the work wasn’t really the first, just the one that published. another example is the Wheatstone bridge. [Sir Charles Wheatstone] made it famous, but it was actually the brainchild of [Samuel Christie].
和？
For some reason, everyone knows Ohm’s law, but you don’t hear much about poor old [Gustav]. If you take an electrical engineering class, these laws are among the first things you learn. You might not use it every day, especially in this day of computer simulations. However, understanding analysis like this can help you develop an intuitive understanding of electronics.
By the way, the simulations in this post are using the Falstad simulator we’ve covered before. While it is common to use a simulator to just give you answers, it is also helpful to let it check your work. The equations above, for example, would be easy to mix up signs or make another mistake. If the answer doesn’t match the simulator, you probably made a mistake. Sure, you can just read the value off the simulator, but that doesn’t let you develop the intuition that working through the math will.