CBSE Class 12 Physics Capacitance Solved Examples

Ex. 1 The capacitor of capacitance 4μF and 6μF are connected in series. A potential difference of 500 volts is applied to the outer plates of the two capacitor system. Then the charge on each capacitor is numerically-
(A) 6000 C (B) 1200C (C) 1200 μC (D) 6000μC

Sol. CR =C₁C₂/C₁+C₂ + = 2.4 μF
Charge flown through the circuit
= 2.4 × 500 × 10^–6C = 1200 μC
Ans.[C]

Ex. 2 Three capacitors are connected to D.C. source of 100 volts as shown in the adjoining figure. If the charge accumulated on plates of C1, C2 and C3 are qa , qb , qc , qd , qe and qf respectively, then

Sol. In series combination, charge is same on capacitor. Ans.[D]

Ex.3 Three capacitors each of capacitance 1μF are connected in parallel. To this combination, a fourth capacitor of capacitance 1μF is connected in series. The resultant capacitance of the system is-
(A) 4μF (B) 2μF (C) 4/3 μF (D) 3/4 μF
Sol. Resultant of parallel combination
= 3 × 10^–6 μF Total capacitance of combination is
1/Cr = 1/3 x 10 ^-6 =4/3  × 10⁶
⇒ Cr =3/4 μF

Ans.[D]

Ex. 4 In the circuit diagram shown in the adjoing figure, the resultant capacitance between P and Q is-

Ex.5 Four condensers each capacity 4μF are connected as shown in figure VP – VQ = 15 volts. The energy stored in the system is-
(A) 2400 ergs (B) 1800ergs (C) 3600 ergs (D) 5400 ergs

Sol. Total capacitance of given system]
1/ C_R= 5/8  ⇒ C_R = 8/5  μF

Energy stored =1/2 C_RV²
= 1/2  ×8/ 5× 10^–6 × 225
= 180 × 10^–6 joule
= 180 × 10^–6 × 10⁷ ergs
= 1800 ergs

Ans.[B]

Ex.6 Two capacitors each of 0.5 μF capacitance are connected in parallel and are then charged by 200 volts. D.C. supply. The total energy of their charges (in joules) is-
(A) 0.01 (B) 0.02
(C) 0.04 (D) 0.06

Ex.8 Four capacitors are connected as shown in the adjoining figure. The potential difference between A and B is 1500 volts. The energy stored in 2μF capacitance will be-

Ex.9 Four capacitors of each capacity 3μF are connected as shown in the adjoining figure. The ratio of equivalent capacitance between A and B and between A and C will be-

Please click on below link to download pdf file for CBSE Class 12 Physics Capacitance Solved Examples.