NCERT Class XII Chapter
Electrostatic Potential and Capacitance
Questions With Solutions
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Question : 25
Total: 37
Obtain the equivalent capacitance of the network in figure. For a 300 V supply, determine the charge and voltage across each capacitor.
Solution:
Since C 2 and C 3 are in series, so, C' = 100 pF
SinceC 1 and C' are parallel
so C" =C 1 + C' = 100 + 100 or C" = 200 pF
SinceC 4 and C" are in series, so net capacitance of the network is
=
+
=
+
=
or C 2 =
pF = 66.7 pF
Net charge stored on the combination is
Q = CV =
× 10 − 12 × 300 = 2 × 10 − 8 C
As C″ andC 4 are in series, so Q" = Q 4 = Q or Q" = Q 4 = 2 × 10 − 8 C
and hence V" =
=
= 100 V
andV 4 =
=
= 200 V
SinceC 1 and C' are in parallel, so
V 1 = V' = V" or V 1 = V' = 100 V
and henceQ 1 = C 1 V 1 = 100 × 10 − 12 × 100 = 1 × 10 − 8 C
and Q' =C 1 V 1 = 100 × 10 − 12 × 100 = 1 × 10 − 8 C
and Q' = C'V' = 100 ×10 − 12 × 100 = 1 × 10 − 8 C
SinceC 2 and C 3 are in parallel, so Q 2 = Q 3 = Q' or Q 2 = Q 3 = 1 × 10 − 8 C and hence V 2 =
=
= 50 V
andV 3 =
=
= 50 V
Since
so C" =
Since
Net charge stored on the combination is
Q = CV =
As C″ and
and hence V" =
and
Since
and hence
and Q' =
and Q' = C'V' = 100 ×
Since
and
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