What is the charge stored when 12.50 volts is applied to a 5.00-picofarad capacitor?
In this example, we have three quantities that we want to connect: charge, voltage, and capacitance. There is a mathematical equation that does just that. It says that the capacitance of a capacitor is equal to the charge on the capacitor divided by the voltage across it.
In our case of course, we don’t want to solve for capacitance. But we do want to solve for charge 𝑄. So we multiplied both sides of this equation by the voltage 𝑉. And we find that 𝑄 is equal to 𝐶 times 𝑉.
To solve for 𝑄, now it’s just a matter of correctly plugging in for the capacitance and voltage. Recalling our prefixes, we write 5.00 picofarads as 5.00 times 10 to the negative 12th farads. And our voltage is 12.50 volts.
This product comes out as 0.0625 nanocoulombs. That’s the amount of charge stored on this capacitor with a potential difference of 12.50 volts across it.