Question

Which one is the not correct expression for energy stored in a capacitor (a) ½ CV2 (b) Q 2 /2C (c) ½ QV (d) QV2​

Answer 1

Answer: d) QV/2

Explanation:

Answer 2

Answer:

So , incorrect expression for energy is option (d)  $QV^{2}$ .

Explanation:

Energy stored in the capacitor is in form of work done .

work done in storing charge Q in capacitor with capacitance C with potential supply V is given by following relation .  

          dw= Vdq    ------(i)      we also k

now  Q= CVfrom this

V = Q/C putting in eq (i)  

   $dw = \frac{Q}{C} dq$    

 $\int\limits^ {}\ dw = \int\limits^{} {\frac{Q}{C} } \, dq$    

    $w= \frac{Q^{2} }{2C}$-------(ii)substituting

Q= cv in(ii)        

 $w=\frac{V^{2}C }{2}$

Substituting C= Q/V in (ii)

$w=\frac{QV}{2}$

Hence work done is given by   $\frac{Q^{2} }{2C}$ ,  $\frac{V^{2}C }{2}$  , $\frac{QV}{2}$.