# Magic

In my second time teaching (2007-2008), the magic disappeared because the unknowns had disappeared.

To get magic, you have to jump into the unknowns/future.

— Me@2013-12-31 5:34 PM

# V 和 U 的分別

Electric Potential and Electric Potential Energy

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electric potential = electric potential energy per unit charge

 V=\frac{U}{Q}

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 \frac{1}{4 \pi \epsilon_0} \frac{Q_1 Q_2}{r}

 \frac{1}{4 \pi \epsilon_0} \frac{Q}{r}

— Me@2014.01.04