Notes
An inductor resists changes in current: $\displaystyle \varepsilon=-L\frac{dI}{dt}$.
- Energy stored: $\displaystyle U=\frac{1}{2}LI^2$.
- Solenoid: $L=\mu_0n^2A\ell$.
Practice
$L=2$ H and current changes at 3 A/s. emf magnitude:
$\displaystyle L\frac{dI}{dt}$.
Energy in a 4 H inductor carrying 3 A:
$\displaystyle \frac{1}{2}(4)(9)$.
An inductor opposes:
Self-induction.
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