Question

Can someone please explain where this equation comes from?

Answer 1

You find the electron's velocity from conservation of energy;
(1/2)mv^2 = qV
v = SqRt[2qV/m]



Where does qV come from?

I understand that the magnetic force is
$$\overrightarrow{F_{B}} = q(\overrightarrow{V}x\overrightarrow{B})$$

And that

$$\overrightarrow{F} = ma$$

So how does it turn into the 1st equation when setting them equal to each other?

Answer 2

So the conservation of energy is:

$$KE_{i} + PE_{i} = KE_{f} + PE_{f}$$

And I know $$KE = \frac{1}{2}mv^{2}$$

Answer 3

But charge $$q$$ times the velocity vector $$\overrightarrow{V}$$ ?