Question

Read Example 26.4 - Reconnection of Capacitors A Consider the following circuit. Let C= 14 F, C = 121F, and 4V = 30 Volt. Notice the capacitors are connected with their plates at opposite polarity. 511 10 1. Ifa 30 volt battery is used to charge each capacitor separately, what is the initial charge on each capacitor? QUE 2. Now consider the switches to be closed: esta G b a) Which way will charges move? b) How will the charges know when to stop moving? c) What will happen at the negative plate of C, when charges arrive at it? __ d) How does this explain the change in polarity of C? - 3. Why can't this problem be treated as a set of parallel capacitors?

the whole thing please

Answer 1

C1 = 14 x 10^(-6) F . C2 = 12 x 10^(-6) F

V = 30 V

Q1 = C1 V = 14 x 10^(-6) F x 30 V = 420 x !0^(-6) C

Q2 = C2 V = 12 x 10^(-6) F x 30 V = 360 x 10^(-6) C

when connected in parallel with opposite polarity plates

Net charge = Q1-Q2 = 60 x 10^(-6) C

Vf = [60 x 10^(-6) C]/ [( 14+12) x 10^(-6) F] = (60/26 )V . ( Vf = Final voltage between terminals a and b)

Q1f = 14 x 10^(-6) F x (60/26) V =32 x 10^(6) C ( Q1f = Final charge on capacitor1)

Q2f = 12 x 10^(-6) x (60/26) V = 28 x 10^(6) C ( Q2f = Final charge on capacitor 2)

a)

+ charge moved to negative terminal and neutralised the charge there , and left over positive charge is shared in proportion of their respective capacitances.

b)

Charges move till + charge ( which is higher than - charge) neutralises entire negative charge and then further + charge moves on to C2 till  the potentials across both capacitors are equalised.

c)

Charges at negative plate are neutralised in entirety and thereafter the c2 gets charged positive

d)

Change in polarity is inevitable if both plates which are connected together have to be at same potential finally.

3. This not a parallel connection, since in parallel connection positive terminals of both capacitors are connected and similarly negative terminals are also connected together.