Combinations of Capacitors Energy Stored in a Charged

-Combinations of Capacitors -Energy Stored in a Charged Capacitor AP Physics C Mrs. Coyle

Circuit Symbols used in Circuit Diagrams Resistor

Capacitors in Parallel • The potential difference across the capacitors is the same. • The flow of charges ceases when the voltage across the capacitors equals that of the battery. • The total charge of the capacitors in series is the sum of the individual charges.

Equivalent Capacitance for Capacitors in Parallel n n Ceq is greater than any of the individual capacitors C. It is as if the areas of the capacitors were combined.

Capacitors in Series n n n Electrons are transferred from the left plate of C 1 to the right plate of C 2 through the battery An equal amount of negative charge is removed from the left plate of C 2, leaving it with an excess positive charge All of the right plates gain charges of –Q and all the left plates have charges of +Q

Equivalent Capacitance for Capacitors in Series The equivalent capacitance of a series combination is always less than any individual capacitor in the combination.

Ex: Find the equivalent capacitance, the charge and the voltage across in one of the 2μF capacitors. 6 V Ans: 8 μF, 6 μC

Ex 26. 4: Find the Equivalent Capacitance Answer: 6 m. F

Work to Charge a Capacitor n The work needed to transfer a charge, q, from one plate to the other through the battery is: n The total work required to charge the capacitor from q=0 to Q is:

Energy Stored in a Capacitor n The work done in charging the capacitor is stored as electric potential energy U: n This applies to a capacitor of any geometry. The energy stored increases as the charge increases and as the potential difference increases. At a certain maximum voltage, corona discharge occurs between the plates. n n

Energy and Energy density for a Parallel Plate Capacitor n Energy density (energy per unit volume)