# Electronic – how to charge a steel ball

charge

I have a 2 mm radius steel ball and I want to charge it in a 0.025 Coulomb charge. Can I do that domestically or the charge is too high? And how can I do that assuming I don't have another conductive material that I know it's charge?

#### Best Answer

Not if you value your life!. The capacitance of a sphere is given by :-

\$C=4\pi\epsilon_0R\$

The voltage on a capacitor is given by :-

\$V=\dfrac{Q}{C}\$

Putting your figures into those equations we find that the capacitance of your sphere is about 0.22pF and the voltage required for that much charge would be 110GV!

Edit ...

If you had another conductive object, you could make a two-plate capacitor in which case the required voltage could be much lower, so in theory you could charge a two plate capacitor using a much lower voltage, then move the other plate away and this would leave your original sphere charged, but this charge would soon leak away.