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## Homework Statement

## Homework Equations

##\omega = v/r##

##q\vec v \times \vec B\ =\ \vec F_B##

##|\vec F|d\ =\ |\vec E|##

##q \Delta V\ =\ E##

## The Attempt at a Solution

(So, my answer is twice and large as the correct answer. This is the second time this has happened on a question like this . . .)

Since a negative charge would collect on the outside of the disk I began by analyzing one negative charge and treated it in equilibrium on the edge of the disk,

$$\begin{align}

q\vec v \times \vec B- \frac{|\vec E|}{d}\ &=\ 0 \\

qvB \ &=\ \frac{q \Delta V}{r} \\

vBr \ &=\ \Delta V

\end{align}$$

And since ##v\ =\ \omega r##:

$$\begin{align}

(\omega r)Br \ &=\ \Delta V \\

\Delta V \ =\ \epsilon \ &\approx\ 48.3\ V

\end{align}$$

Any help would be wonderful c: