- #1
richyw
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Homework Statement
A solid conducting disk of radius a rotates about its symmetry axis with
angular speed ω rads/s. If there is a uniform magnetic field [itex]\mathbf{B}[/itex] perpendicular to the disk derive an expression for the potential difference induced between the centre of the disk and its rim.
Homework Equations
[tex]f_{\text{mag}}=\mathbf{v}\times\mathbf{r}[/tex]
[tex]\epsilon=\oint \mathbf{f}\dot d\mathbf{l}[/tex]
[tex]\Delta V=\int^{\mathbf{b}}_{\mathbf{a}}\mathbf{E}\cdot d\mathbf{l}[/tex]
The Attempt at a Solution
I found the force per unit charge
[tex]f_{\text{mag}}=\mathbf{v}\times\mathbf{r}[/tex][tex]\mathbf{v}=\mathbf{\omega}\times\mathbf{r}=\omega r\hat{\phi}[/tex]
[tex]f_{\text{mag}}=\omega r\hat{\phi}\times\mathbf{r}=\omega r B \hat{r}[/tex]
Then I thought I could use
[tex]\epsilon=\oint \mathbf{f} \cdot d\mathbf{l}[/tex]
and get [tex]\epsilon=2\pi B\omega r^2[/tex] which would give a potential difference of [tex]2\pi B\omega a^2[/tex]
but this is wrong. I think I have [itex]f_{\text{mag}}[/itex] correct. So now how do I find the potential difference?