AP Physics C: Electricity and Magnetism / Unit 11: Electric Circuits
11.1 Electric Current
Notes
$$I=\frac{dQ}{dt},\qquad I=nqv_dA,\qquad J=\frac{I}{A}$$
- Drift velocity is very slow, but the field travels at nearly light speed.
Practice
$Q(t)=3t^2$ C. Current at $t=2$ s:
$\displaystyle I=\frac{dQ}{dt}=6t$.
Electron drift velocity in a wire is:
Many collisions.
Current density is:
$\displaystyle J=\frac{I}{A}$.
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