# A sphere of radius 10 mm that carries a charge of 8nC is attached at the end of an insulating string and is whirled in a circle. The rotation frequency is 100? rad/s. What average current does this rotating charge represent ?

${I}_{tot}={\int}_{0}^{\mathrm{\pi}}\omega r\mathrm{sin}\theta \delta =\omega r\delta {\int}_{0}^{\mathrm{\pi}}\mathrm{sin}\theta =2\omega r\delta $

Now we have r=10mm=.01m and $\omega =100\text{rad/s}$, so we have

$I=2\times 0.01\times 100\times 6.4\times {10}^{-8}=1.28\times {10}^{-7}$A

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