A parallel plate capacitor is made of two plates of length $l$, width $w$ and separated by distance $d$. A dielectric slab ( dielectric constant $K$) that fits exactly between the plates is held near the edge of the plates. It is pulled into the capacitor by a force $F = -\frac{{\partial U}}{{\partial x}}$ where $U$ is the energy of the capacitor when dielectric is inside the capacitor up to distance $x$ (See figure). If the charge on the capacitor is $Q$ then the force on the dielectric when it is near the edge is
A parallel plate capacitor is made of two plates of length $l$, width $w$ and separated by distance $d$. A dielectric slab ( dielectric constant $K$) that fits exactly between the plates is held near the edge of the plates. It is pulled into the capacitor by a force $F = -\frac{{\partial U}}{{\partial x}}$ where $U$ is the energy of the capacitor when dielectric is inside the capacitor up to distance $x$ (See figure). If the charge on the capacitor is $Q$ then the force on the dielectric when it is near the edge is
- [JEE MAIN 2014]
- A
$\frac{{{Q^2}d}}{{2w{l^2}{\varepsilon _0}}}K$
- B
$\frac{{{Q^2}w}}{{2d{l^2}{\varepsilon _0}}}\left( {K - 1} \right)$
- C
$\frac{{{Q^2}d}}{{2w{l^2}{\varepsilon _0}}}\left( {K - 1} \right)$
- D
$\frac{{{Q^2}w}}{{2d{l^2}{\varepsilon _0}}}K$
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- [AIIMS 2009]
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