Question

Assertion :Physically, if a dielectric with a high value of k is placed in an electric field, the electric field will be greatly reduced inside. Reason: Dielectrics are very useful in modern electronics as it is possible to to precisely control their permittivity by doping them with other types of materials.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

If a dielectric is placed in an electric field, the electric field reduces due to the opposite field produced in dielectric by the process of polarisation. The electric field reduces by the factor $\kappa$ (dielectric constant of dielectric), so if $\kappa$ is high, field will be reduced greatly.

Now, doping of dielectric materials changes their dielectric properties very much, which are very useful in microelectronics. For e.g. when $Si{O}_2$ is doped with fluorine, its dielectric constant (relative permittivity) decreases.

Therefore reason of assertion is polarisation. Hence both, assertion and reason are correct but reason is not correct explanation for assertion.