NEET-XII-Physics
qstns with ansrs year:2022
- #40A capacitor of capacitance `` C =900 \,pF `` is charged fully by `` 100\, V `` battery `` B `` as shown in figure (a). Then it is disconnected from the battery and connected to another uncharged capacitor of capacitance `` C =900 \,pF `` as shown in figure (b). The electrostatic energy stored by the system (b) is :
(A) `` 1.5 \times 10^{-6} J ``
(B) `` 4.5 \times 10^{-6} J ``
(C) `` 3.25 \times 10^{-6} J ``
(D) `` 2.25 \times 10^{-6} J ``digAnsr: DAns :
Common potential
`` V _{ C } =\frac{ C _{1} V _{1}+ C _{2} V _{2}}{ C _{1}+ C _{2}} ``
`` =\frac{ C \times 100+ C \times 0}{ C + C } ``
`` =50 `` Volt
Electrostatic energy stored
`` =2 \times \frac{1}{2} CV ^{2}= CV ^{2} ``
`` =900 \times 10^{-12} \times 50 \times 50 ``
`` =225 \times 10^{-8} J ``
`` =2.25 \times 10^{-6} J ``