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JEE Main 2013 · Units & Dimensions

Units & Dimensions question from JEE Main 2013

Q86JEE Main 2013Easy

Units & Dimensions

Let [ε0\varepsilon_0] denote the dimensional formula of the permittivity of vacuum. If M = mass, L = length, T = time and A = electric current, then:

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Answer: (b)

  1. Coulomb's law: F=q24πε0r2F = \frac{q^2}{4\pi\varepsilon_0 r^2}, so ε0=q2Fr2\varepsilon_0 = \frac{q^2}{Fr^2}.
  2. [ε0]=A2T2MLT−2⋅L2=M−1L−3T4A2[\varepsilon_0] = \frac{\mathrm{A^2T^2}}{\mathrm{MLT^{-2}}\cdot\mathrm{L^2}} = \mathrm{M^{-1}L^{-3}T^4A^2}
  3. So the answer is (b).
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