📈 法拉第定律：变化越快，电越强📈 Faraday's Law: The Faster the Change, the Stronger the Current
上一片里，磁铁一动、电流表的指针就动了——但动得多快、绕了几圈，指针偏多少，上一片没说。这一片给你精确的账本：法拉第定律。Last leaf, the moment the magnet moved, the needle moved — but how far it swings was left unsaid. This leaf opens the exact rulebook: Faraday's law.
第 1 步：快慢才是开关Step 1: Speed is the switch
磁铁只是“动”还不够——动得越快，电流会怎样？Moving is not enough — what does moving faster do?
同一块磁铁，慢慢插进线圈：指针懒洋洋地只挪一格；抓起来飞快地来回甩：指针直接打到满格。感应电动势跟“磁通量变化的快慢”成正比——速度翻倍，电压也翻倍。“变化快慢”就是电流的大小开关。Same magnet pushed in slowly: the needle barely creeps. Swung back and forth at full speed: the needle slams to full scale. The induced EMF is proportional to how fast the magnetic flux changes — double the speed, double the voltage. The rate of change is the switch.
速度已经拉满，还能不能更猛一点？Speed maxed out — can we go even stronger?
第 2 步：匝数是放大器Step 2: Turns are the amplifier
能。线圈每绕一圈，就像一路微型发电机；N 匝串起来，电压、电流都乘 N。同样一块磁铁、同样的速度：单匝只亮一点点，十匝就是十倍。匝数和速度，是两个各自独立的旋钮。Yes. Every turn of the coil acts like one tiny generator; N turns in series multiply voltage and current by N. Same magnet, same speed: one turn lights it barely, ten turns light it ten times over. Turns and speed are two independent knobs.
这么说，发电厂就是把“磁铁 + 线圈”放大了一万倍？So a power plant is just this magnet-and-coil, scaled up?
第 3 步：水电站的转速旋钮Step 3: The speed knob at a hydropower station
正是。水电站里，水流推着水轮机转，水轮机带着磁铁在线圈里高速旋转，磁通量一刻不停地变化，电就源源不断地来了。转速越高，电压越高——调度员真正在调的，就是这个转速。Exactly. At a hydropower station, water spins the turbine, the turbine spins a magnet inside coils, the flux never stops changing, and electricity pours out. Higher speed, higher voltage — that spin rate is the knob operators really turn.
🎮 你来当转速调度员（1 分钟）🎮 Your turn: the speed dispatcher (1 minute)
两个旋钮已经装好：磁铁速度 v、线圈匝数 N。按任务提示，把电流表拉到达标线，4 关全过。Two knobs are ready: magnet speed v and coil turns N. Follow each mission and push the needle to its target — clear all 4.
一句话记住它：法拉第定律——感应电动势 ∝ 磁通量变化的快慢；动得越快、匝数越多，电越强。Remember it in one line: Faraday's law — induced EMF ∝ rate of change of magnetic flux; faster motion and more turns both mean stronger current.
感应电动势和“变化快慢”成正比：速度翻倍，电压翻倍EMF is proportional to the rate of change: double the speed, double the voltage匝数是乘法：N 匝串联，电压、电流都 ×NTurns multiply: N turns in series raise voltage and current ×N发电机就是它：转速越高，发的电压越高This is every generator: higher spin, higher voltage
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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