JEE Mains · Physics · STD 12 - Electric potential and capacitance
- JEE Mains 2024
- Hard
- MCQ
Two identical capacitors have same capacitance \(C\). One of them is charged to the potential \(\mathrm{V}\) and other to the potential \(2 \mathrm{~V}\). The negative ends of both are connected together. When the positive ends are also joined together, the decrease in energy of the combined system is _______.
Pick an option to check your answer.
Answer & Solution
Correct Answer
(A) \(\frac{1}{4} \mathrm{CV}^2\)
Step-by-step Solution
Detailed explanation
\(\mathrm{V}_{\mathrm{C}}-\frac{\mathrm{q}_{\text {net }}}{\mathrm{C}_{\text {net }}}=\frac{\mathrm{CV}+2 \mathrm{CV}}{2 \mathrm{C}}\)
\(\mathrm{V}_{\mathrm{C}}=\frac{3 \mathrm{~V}}{2}\)
Loss of energy
\(=\frac{1}{2} \mathrm{CV}^2+\frac{1}{2} \mathrm{C}(2 \mathrm{~V})^2-\frac{1}{2} 2 \mathrm{C}\left(\frac{3 \mathrm{~V}}{2}\right)^2\)
\(=\left(\frac{\mathrm{CV}^2}{4}\right)\)
More questions from Physics
- If speed \((V)\), acceleration \((A)\) and force \((F)\) are considered as fundamental units, the dimension of Young’s modulus will beJEE Mains 2023 Hard
- Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : A electron in a certain region of uniform magnetic field is moving with constant velocity in a straight line path.
Reason (R): The magnetic field in that region is along the direction of velocity of the electron. In the light of the above statements, choose the correct answer from the options given below :JEE Mains 2025 Medium - A current of \(10\, A\) exists in a wire of crosssectional area of \(5\, mm ^{2}\) with a drift velocity of \(2 \times 10^{-3}\, ms ^{-1}\). The number of free electrons in each cubic meter of the wire is ..........JEE Mains 2021 Medium
- A bead of mass \(m\) stays at point \(P ( a , b )\) on a wire bent in the shape of a parabola \(y=4 Cx ^{2}\) and rotating with angular speed \(\omega\) (see figure). The value of \(\omega\) is (neglect friction)
JEE Mains 2020 Hard - A particle \(P\) is formed due to a completely inelastic collision of particles \(x\) and \(y\) having de -Broglie wavelengths \({\lambda _x}\) and \({\lambda _y}\) respectively. If \(x\) and \(y\) were moving in opposite directions, then the de -Broglie wavelength of \(P\) isJEE Mains 2019 Medium
- A cylinder with fixed capacity of \(67.2\, lit\) contains helium gas at \(STP\). The amount of heat needed to raise the temperature of the gas by \(20\,^oC\) is ..... \(J\) [Given that \(R = 8.31\, J\, mol^{-1}\, K^{-1}\)]JEE Mains 2019 Medium
More PYQs from JEE Mains
- With what speed should a galaxy move outward with respect to earth so that the sodium-D line at wavelength \(5890\) \(\stackrel{\circ}{{A}}\) is observed at \(5896\) \(\stackrel{\circ}{{A}}\) ? (in \({km} / {sec}\))JEE Mains 2021 Medium
- Light wave traveling in air along \(x\)-direction is given by \(E _{ y }=540 \sin \pi \times 10^{4}( x - ct ) Vm ^{-1}\). Then, the peak value of magnetic field of wave will be \(\dots \times 10^{-7}\,T\) (Given \(c =3 \times 10^{8}\,ms ^{-1}\) )JEE Mains 2022 Easy
- A particle starts moving from time \(t=0\) and its coordinate is given as \(x(t)=4t^{3}-3t.\)
A. The particle returns to its original position (origin) 0.866 units later
B. The particle is 1 unit away from origin at its turning point.
C. Acceleration of the particle is non-negative.
D. The particle is 0.5 units away from origin at its turning point.
E. Particle never turns back as acceleration is non-negative.
Choose the correct answer from the options given below :JEE Mains 2026 Hard