考前速记 Last Minute Summary

核心公式 Key Formulas

$x = x_0 \sin\omega t$ $I_{\text{r.m.s.}} = \frac{I_0}{\sqrt{2}}, \quad V_{\text{r.m.s.}} = \frac{V_0}{\sqrt{2}}$ $\langle P \rangle = \frac12 P_{\text{max}} = I_{\text{r.m.s.}}^2 R = \frac{V_{\text{r.m.s.}}^2}{R}$

考前 Checklist

• Peak $(\times\sqrt{2})$ vs r.m.s. $(\div\sqrt{2})$ — 分清！
• Half-wave rectification: 1 diode, removes half cycle
• Full-wave rectification: 4 diodes (bridge), reverses half cycle
• Smoothing: capacitor charges at peak, discharges through $R$
• $\tau = RC$ — larger $\tau$ = better smoothing but slower response
• Mean power for sinusoidal a.c. is half maximum power
• Power is always positive — graph stays above zero