JEE Mains · Physics · STD 12 - 2. Electric potential and capacitance
A capacitor with capacitance \(5\,\mu F\) is charged to \(5\,\mu C.\) If the plates are pulled apart to reduce the capacitance to \(2\,\mu F,\) how much work is done?
- A \(3.75\times 10^{-6}\,J\)
- B \(2.55\times 10^{-6}\,J\)
- C \(6.25\times 10^{-6}\,J\)
- D \(2.16\times 10^{-6}\,J\)
Answer & Solution
Correct Answer
(A) \(3.75\times 10^{-6}\,J\)
Step-by-step Solution
Detailed explanation
Work done \(=\Delta U\) \( = {U_t} - {U_i}\) \( = \frac{{{q^2}}}{{2{C_r}}} - \frac{{{q^2}}}{{2{C_i}}}\) \( = \frac{{{{\left( {5 \times {{10}^{ - 6}}} \right)}^2}}}{2}\left( {\frac{1}{{2 \times {{10}^{ - 6}}}} - \frac{1}{{5 \times {{10}^{ - 6}}}}} \right)\)…
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Physics
- In an experiment, a set of reading are obtained \(-1.24 mm, 1.25 mm, 1.23 mm, 1.21 mm\). The expected least count of the instrument used in recording these readings is ___________ mm.JEE Mains 2026 Medium
- A letter \('A'\) is constructed of a uniform wire with resistance \(1.0\,\Omega \) per \(cm\) , The sides of the letter are \(20\, cm\) and the cross piece in the middle is \(10\, cm\) long. The apex angle is \(60\) . The resistance between the ends of the legs is close to ................ \(\Omega\)JEE Mains 2013 Hard
- There is a circular tube in a vertical plane. Two liquids which do not mix and of densities \(d_1\) and \(d_2\) are filled in the tube. Each liquid subtends \(90^o\) angle at centre. Radius joining their interface makes an angle \(\alpha\) with vertical. Ratio \(\frac{{{d_1}}}{{{d_2}}}\) is
JEE Mains 2014 Hard - For an electromagnetic wave propagating through vacuum, \(\vec{k}\), \(\vec{E}\) and \(\omega\) represent propagation vector, electric field and angular frequency, respectively. The magnetic field associated with this wave is represented by :JEE Mains 2026 Medium
- Find the distance of the image from object \(O\), formed by the combination of lenses in the figure : (in \(cm\))
JEE Mains 2021 Hard - A thin metallic wire having cross sectional area of \(10^{-4} \mathrm{~m}^2\) is used to make a ring of radius \(30 \mathrm{~cm}\). A positive charge of \(2 \pi \mathrm{C}\) is uniformly distributed over the ring, while another positive charge of \(30\) \(\mathrm{pC}\) is kept at the centre of the ring. The tension in the ring is__________ \(\mathrm{N}\); provided that the ring does not get deformed (neglect the influence of gravity). (given, \(\frac{1}{4 \pi \epsilon_0}=9 \times 10^9 \mathrm{SI}\) units)JEE Mains 2024 Hard
More PYQs from JEE Mains
- Let the line \(\ell: x =\frac{1- y }{-2}=\frac{ z -3}{\lambda}, \lambda \in R\) meet the plane \(P : x +2 y +3 z =4\) at the point \((\alpha, \beta, \gamma)\). If the angle between the line \(\ell\) and the plane \(P\) is \(\cos ^{-1}\left(\sqrt{\frac{5}{14}}\right)\), then \(\alpha+2 \beta+6 \gamma\) is equal toJEE Mains 2023 Hard
- A circle of radius \(2\) unit passes through the vertex and the focus of the parabola \(y^{2}=2 x\) and touches the parabola \(y=\left(x-\frac{1}{4}\right)^{2}+\alpha\), where \(\alpha>0\). Then \((4 \alpha-8)^{2}\) is equal toJEE Mains 2022 Hard
- Let the area enclosed by the \(x\)-axis, and the tangent and normal drawn to the curve \(4 x ^{3}-\) \(3 x y^{2}+6 x^{2}-5 x y-8 y^{2}+9 x+14=0\) at the point \((-2,3)\) be \(A\). Then \(8 A\) is equal to \(.......\)JEE Mains 2022 Hard
- If all the words (with or without meaning) having five letters, formed using the letters of the word \(SMALL\) and arranged as in a dictionary; then the position of the word \(SMALL\) is :JEE Mains 2016 Hard
- Two uniform circular discs are rotating independently in the same direction around their common axis passing through their centres. The moment of inertia and angular velocity of the first disc are \(0.1 \;kg - m ^{2}\) and \(10\; rad \,s^{-1}\) respectively while those for the second one are \(0.2 \;kg - m ^{2}\) and \(5\; rad \,s ^{-1}\) respectively. At some instant they get stuck together and start rotating as a single system about their common axis with some angular speed. The Kinetic energy of the combined system is ...........\(J\)JEE Mains 2020 Hard
- If a function \(f(x)\) defined by \(f(x)=\left\{\begin{array}{ll}a e^{x}+b e^{-x}, & -1 \leq x<1 \\ c x^{2}, & 1 \leq x \leq 3 \\ a x^{2}+2 c x, & 3 < x \leq 4\end{array}\right.\) be continuous for some \(a, b, c \in R\) and \(f ^{\prime}(0)+ f ^{\prime}(2)= e ,\) then the value of of \(a\) isJEE Mains 2020 Hard