An electron, accelerated by a potential difference $V=1.0 \mathrm{kV}$, moves in a uniform magnetic field, at an angle $\alpha =30°$, to the vector $B$, whose modulus is $B=29 \mathrm{mT}$. Find the pitch of the helical trajectory of the electron.

A parallel plate capacitor made of circular plates each of radius $R=6.0 \mathrm{cm}$ has a capacitance $\mathrm{C}=100 \mathrm{p}\mathrm{F}.$ The capacitor is connected to a $230 \mathrm{V}$ ac supply with an (angular) frequency of $300\text{\hspace{0.17em}rad\hspace{0.17em}}{\text{s}}^{\text{-1}}$. Determine the amplitude of $\mathrm{B}$ at a point $3.0 \mathrm{cm}$ from the axis between the plates.