In terms of resistance $R$ and time $T$, the dimensions of ratio $\frac{\mu}{\varepsilon}$ of the…

In terms of resistance $R$ and time $T$, the dimensions of ratio $\frac{\mu}{\varepsilon}$ of the permeability $\mu$ and permittivity $\varepsilon$ is:
  1. $\left[\mathrm{RT}^{-2}\right]$
  2. $\left[\mathrm{R}^2 \mathrm{~T}^{-1}\right]$
  3. $\left[\mathrm{R}^2\right]$
  4. $\left[\mathrm{R}^2 \mathrm{~T}^2\right]$

Solution

Dimensions of $\mu=\left[\right.$ MLT $\left.^{-2} \mathrm{~A}^{-2}\right]$ Dimensions of $\in=\left[\mathrm{M}^{-1} \mathrm{~L}^{-3} \mathrm{~T}^4 \mathrm{~A}^2\right]$ Dimensions of $\mathrm{R}=\left[\mathrm{ML}^2 \mathrm{~T}^{-3} \mathrm{~A}^{-2}\right]$ $ \begin{aligned} &\therefore \frac{\text { Dimensions of } \mu}{\text { Dimensions of } e}=\frac{\left[\mathrm{MLT}^{-2} \mathrm{~A}^{-2}\right]}{\left[\mathrm{M}^{-1} \mathrm{~L}^{-3} \mathrm{~T}^4 \mathrm{~A}^2\right]} \\ &=\left[\mathrm{M}^2 \mathrm{~L}^4 \mathrm{~T}^{-6} \mathrm{~A}^{-4}\right]=\left[\mathrm{R}^2\right] \end{aligned} $

Asked in: JEE Main 2014 (11 Apr Online)

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