Discussion Forum



1)

A series R-C circuit is connected to AC voltage source. Consider two cases (A) when C is without a dielectric medium and (B) when C is filled with a dielectric of constant 4. The current IR through the resistor and voltage VC across the capacitor are compared in the two cases. Which of the following is/are true?


A) $I_{R}^{A}$ > $I_{R}^{B}$

B) $I_{R}^{A}$ < $I_{R}^{B}$

C) $V_{C}^{A}$ > $V_{R}^{B}$

D) $V_{C}^{A}$ < $V_{C}^{B}$

Answer:

Option B,C

Explanation:

$Z= \sqrt{R^{2}+X_{C}^{2}}=\sqrt{R^{2}+\left(\frac{1}{\omega C}\right)^{2}}$

In case (b) capacitance C will be more. Therefore, impedance Z will be less.
Hence, current will be more.

$\therefore$ Option(b) is correct 

 Further   $V_{C}=\sqrt{V^{2}-V_{R}^{2}}$

                         $\sqrt{V^{2}-(IR)^{2}}$

 In case (b), since current l is more

 Therefore  , $V_{C}$ will be less

 $\therefore$  Option (c) is correct

$\therefore$  Correct options are (b) and (c)