Question
L, C and R represent the physical quantities inductance, capacitance and resistance respectively. Which of the following combinations have dimensions of frequency?

  1. $\frac{1}{\text{RC}}$

  2. $\frac{\text{R}}{\text{L}}$

  3. $\frac{1}{\sqrt{\text{LC}}}$

  4. $\text{C}/\text{L}$

Answer

  1. $\frac{1}{\text{RC}}$

  2. $\frac{\text{R}}{\text{L}}$

  3. $\frac{1}{\sqrt{\text{LC}}}$

Explanation:

þ Time constant t = RC in RC circuit

frequency $=\frac{1}{\tau}=\frac{1}{\text{RC}} \ ...(\text{i})$

þ Time constant in LR circuit is $\tau=\frac{\text{L}}{\text{RC}}$

frequency $\frac{1}{\tau}=\frac{\text{R}}{\text{L}} \ ...(\text{ii})$

þ eq. (i) & (ii) multiply

frequency $=\frac{1}{\text{LC}}$

frequency $=\frac{1}{\sqrt{2\text{C}}}$

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(Image)

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