Question

Two parallel plate capacitors of capacitances C₁  and C₂ such that C₁ = 2C₂ are connected across a  battery of V volts as shown in the figure. Initially  the key (k, is kept closed to fully charge the  capacitors. The key is now thrown open and a  dielectric slab of dielectric constant  'K' is inserted  in the two capacitors to completely fill the gap  between the plates. Find the ratio of 

(i) the net  capacitance and 

(ii) the energies stored in the  combination, before and after the introduction  of the dielectric slab.

Comments

Firstly when it is connected with battery the combination is called as parallel combination and when the battery is removed the connection is called as series combination so how in both cases we can use the parallel combination concept and take the answer. So I have the doubt that we should use first parallel combination concept and second series combination concept to get the result.

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But why are removing battery . It us not said in the question.  If you will do it in examination then , it will waste your time and may you also get a decrease in your marks ..but i am not sure. So ask any marks rekated question to your teachers or tutors..

Answer 1

(i) Net capacitance before filling the gap with dielectric slab C_initial = C₁ +  C₂ = 2C₂ + C₂ = 3C₂