考前速记 Last Minute Summary

核心公式 Key Formulas

$F = BIL\sin\theta \quad \text{(载流导体)}$ $F = BQv\sin\theta \quad \text{(运动电荷)}$ $V_H = \frac{BI}{ntq} \quad \text{(Hall voltage)}$ $\Phi = BA \quad \text{(magnetic flux)}$ $E = \frac{\Delta(N\Phi)}{\Delta t} \quad \text{(Faraday's law)}$

考前 Checklist

• Tesla 定义: "newton per ampere per metre"
• Magnetic flux: "product of flux density and cross-sectional area perpendicular to the field"
• Lenz's law: "direction of induced e.m.f. opposes the change producing it"
• Faraday's law: "magnitude of induced e.m.f. proportional to rate of change of flux linkage"
• 单位转换: 1 cm = $10^{-2}$ m, 1 mm = $10^{-3}$ m
• 线圈面积: $A = \pi r^2$, 用半径不是直径
• 磁场线图: 长直导线 → 同心圆，间距增大，注意方向
• 涡电流解释: 先有变化磁场 → e.m.f. → eddy current → force