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Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsElectrostatic Potential and Capacitance1 Mark
Question
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): When air between the plates of a parallel plate condenser is replaced by an insulating medium of dielectric constant its capacity increases.
Reason (R): Electric field intensity between the plates with dielectric in between it is reduced.
✓

Answer

  1. Both A and R are true, and R is the correct explanation of A.
Explanation:

The capacity of a parallel plate condenser is given by,

$\text{C}=\frac{\text{q}}{\text{V}}$ (i)

Electric field intensity becomes $\frac{1}{\text{K}}$ times [as $\text{K}=\frac{\text{E}_0}{\text{E}},$] therefore potential V also becomes $\frac{1}{\text{K}}$ times.

Hence, from equation (i) capacity, becomes K times. Thus electric field decreases and capacitance increases when condenser is filled with insulated medium of some dielectric constant.

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