a 3 mico-farad and 4 micro-farad capacitor are connected in series and charged b

Question

a 3 mico-farad and 4 micro-farad capacitor are connected in series and charged by a 100 volt battery. They are disconnected while fully charged and they are joined by conductors with their positive plates connected to each other and their negative plates connected to each other. Determine the following:
a) the charge on each capacitor when first disconnected from the battery
b) the charge on each capacitor after being reconnected to each other without the battery
c) the voltage on each capacitor after being reconnected
d)the energy stored in each capacitor when first disconnected from the battery
e) the energy stored in each capacitor after being reconnected to each other without the battery
Please also explain how you determine the answers...

Explanation / Answer

Given capcitance of two capacitors            C1 = 3 F   ; C2 =   4 F   initially the capacitors are connected in eries combination           1 / C =   1/ C1 + 1/C2                     = 1/ 3 + 1/ 4     equivalent capacitance              C = 1.71428 F    if the capaciotrs are in series combination charge n each capaciotr is same              Q = C V                   = ( 1.71428F ) ( 100 )                   = 171.4288 C ____________________________________________________________   disconnected while fully charged and they are joined in parallel ombination              equivalent capacitance is                       Ceq =    C1 + C2                                =    3 F + 4 F                                  = 7 F            potential on each capacitance is                     V = Q / Ceq                            = 171.4288C   / 7 F                             = 24.489 V     charge on C1 is   q1   =   C1 V                                        =   3 F * 24.489                                          = 7.3469 *10 -5 C     charge on C2 is q2   = C2 V                                          = 4 F   * 24.489                                           = 9.7956*10-5     C ______________________________________________________________     voltage on each capacitor after being reconnected
                        V = Q / Ceq                            = 171.4288C   / 7 F                             = 24.489 V ______________________________________________________________ energy stored in each capacitor when first disconnected from the battery
                     U1 = Q 2   / 2C1                      U2 = Q2   / 2 C2   ______________________________________________________________                          = 171.4288C   / 7 F                             = 24.489 V ______________________________________________________________ energy stored in each capacitor when first disconnected from the battery
                     U1 = Q 2   / 2C1                      U2 = Q2   / 2 C2   energy stored in each capacitor after being reconnected to each other without the battery
                     U1 =  q1 2   / 2C1                      U2 = q2 2   / 2 C2                        U2 = q2 2   / 2 C2  

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