When a dielectric material placed in uniform electric field, which of the following option is NOT CORRECT :
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → The free movement of charges in a dielectric is possible
In a dielectric the charges are bound to their atoms and molecules; there are no free charges to move through the material. An external field only displaces these bound charges slightly, which polarises the dielectric.
Option (1) The free movement of charges in a dielectric is not possible — Correct statement (Incorrect). A dielectric has no free charge carriers, so charges cannot move freely through it.
Option (2) The free movement of charges in a dielectric is possible — Incorrect statement (Correct). Free movement of charges is what happens in a conductor; in a dielectric the charges stay bound.
Option (3) The external field induces dipole moment by stretching molecules of dielectrics — Correct statement (Incorrect). In a non-polar molecule the field pulls the positive and negative charge centres apart, which induces a dipole moment.
Option (4) The external field induces dipole moment by re-orienting molecules of dielectrics — Correct statement (Incorrect). Polar molecules already have dipole moments pointing at random; the field turns them partly along itself, giving a net dipole moment.
NCERT (2026-27):
Dielectrics and Polarisation – “Dielectrics are non-conducting substances. In contrast to conductors, they have no (or negligible number of) charge carriers.”
Dielectrics and Polarisation – “… In a dielectric, this free movement of charges is not possible. It turns out that the external field induces dipole moment by stretching or re-orienting molecules of the dielectric.”