# Try this one, it's so cool :D

Two equal metal round plates are placed on small distance $$d$$ in a magnetic field of induction $$B$$ whose field lines are parallel with disc's axis . They are rotateing with same angular veocity $$\omega$$ but in the oposite direction. If the centers of plates are connected with a thin conductive thread and charge density of plate's is $$\sigma(r)$$ where $$r$$ is distance from plates axis find $$\sigma(1 m)$$.

$$B=0.1T$$

$$\omega=1 \frac{rad}{s}$$

$$d=10^{-12}m$$

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