Parallel plates of width and length (along the direction a slab is inserted) are…

PHYSICS · Multi-part · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Electric fields in matter · Electric fields in matter

The Boundary-Value Problem, Ch Energy and force in dielectrics

Problem

Parallel plates of width

b = 0.080\,\mathrm{m}

and length

L_p = 0.12\,\mathrm{m}

(along the direction a slab is inserted) are separated by a gap

d = 0.50\,\mathrm{mm}

. They are charged to a potential difference

V_0 = 1.5\,\mathrm{kV}

with a dielectric slab of susceptibility

\chi_e = 3.0

just starting to enter the gap, and are then disconnected from the source so that the free charge

Q

on them stays fixed as the slab is pushed further in. ((a)) Find the pulling force on the slab, at fixed charge, just as it starts to enter (

x\to0

). ((b)) Find the pulling force on the slab, at fixed charge, once it is fully inserted (

x=L_p

), and state the factor by which the force has fallen.