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A source of potential difference \mathrm{V} is connected to the combination of two identical capacitors as shown in the figure. When key \mathrm{ ' K '} is closed, the total energy stored across the combination is \mathrm{ E_{1}.} Now key  \mathrm{ ' K '}  is opened and dielectric of dielectric constant \mathrm{ 5} is introduced between the plates of the capacitors. The total energy stored across the combination is now \mathrm{ E_{2}. }The ratio \mathrm{ E_{1} /E_{2}} will be :

Option: 1

\frac{1}{10}


Option: 2

\frac{2}{5}


Option: 3

\frac{5}{13}


Option: 4

\frac{5}{26}


Answers (1)

best_answer

When the key \mathrm{' K '} is closed
The potential drop across C is \mathrm{V}

\mathrm{ E_1=\frac{1}{2} C V^2+\frac{1}{2} C V^2=C V^2 }

When the key \mathrm{ 'K '} is open

\mathrm{E_2=\frac{1}{2} C' v^2=\frac{1}{2}(5 c) v^2 }

\mathrm{\frac{E_1}{E_2}=\frac{c v^2}{\frac{1}{2} c^{\prime} v^2}=\frac{2}{5}}

Hence (2) is correct option.

Posted by

Divya Prakash Singh

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