Sub-units micro-farad and pico-farad

[natural]

1. Homework Statement [/b]
If the p.d across a capacitor is doubled, by what factor does the ehnergy stored change?

Define the farad, the unit of capacitance. Explain the commonly used sub-units micro-farad and pico-farad.

 

[hage567]

What have you done so far? Show your work. What equation might be useful for question #1?

 

[natural]

V = Q/C ? i don't really undersatnd the question

 

[hage567]

V = Q/C ? i don't really undersatnd the question

That's not an equation for energy. You want $$U=(1/2)CV^2$$ where U is the stored energy, C is the capacitance, and V is the potential difference.

It's asking if the potential difference is doubled, how much does the energy stored in the capacitor change. So using that equation, if you double V, what happens to U?

 

[natural]

ooh ok U doubles

 

[hage567]

ooh ok U doubles

NO, look more closely. It's V squared, right?

 

[natural]

increase by 4?

 

[hage567]

That's better.