Question

If the charge on a capacitor is increased by 2 C, the energy stored in it increases by 44%. The original charge on the capacitor is (in C)

• A. 10
• B. 20
• C. 30
• D. 40

Answer 1

Answer: (A)

10

Answer 2

Let initially the charge is $q$ so

$\frac{1}{2} \frac{q^2}{C} = U_i$

And

$\frac{1}{2} \frac{(q+2)^2}{C} = U_f$

Given

$\frac{U_f -Ui}{Ui}\times 100 = 44$

$\frac{(q+2)^2-q^2}{q} = 0.44$

⇒ $q = 10 \;C$