Capacitors in series
Figure shows capacitors C1 and C2 combined
in series.
The left plate of C1 and the right
plate of C2 are connected to two terminals of a battery and have
charges Q and –Q, respectively.
It then follows that the right plate of C1
has charge –Q and the left plate of C2 has charge Q. If this was not so, the
net charge on each capacitor would not be zero.
This would result in an electric field in the
conductor connecting C1and C2. Charge would flow until
the net charge on both C1 and C2 is zero and there is no
electric field in the conductor connecting C1 and C2.
Thus, in the series combination, charges on the two plates (±Q) are the same on
each capacitor.
The total potential drop V across the combination
is the sum of the potential drops V and V across C and C, respectively.
Following the same steps as for the case of two capacitors, we
get the general formula for effective capacitance of a series combination of n capacitors:
Capacitors in parallel
Figure shows two capacitors arranged in parallel. In this case,
the same potential difference is applied across both the capacitors.
But the plate charges (±Q1) on capacitor 1 and the
plate charges (±Q2) on the capacitor 2 are not necessarily the same:
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