arthham

JEE Advanced 2001 · Units and Measurements

A quantity XX is given by ε0LΔVΔt\varepsilon_0 L \frac{\Delta V}{\Delta t} where ε0\varepsilon_0 is the permittivity of the free space, LL is a length, ΔV\Delta V is a potential difference and Δt\Delta t is a time interval. The dimensional formula for XX is the same as that of

Answer: D. current

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Written solution

Step 1: State the given formula and variables.

The quantity XX is defined by the relation:

X=ε0LΔVΔtX = \varepsilon_0 L \frac{\Delta V}{\Delta t}

where ε0\varepsilon_0 is the permittivity of free space, LL is length, ΔV\Delta V is potential difference, and Δt\Delta t is a time interval.

Step 2: Determine the dimensions of each component.

Using the base dimensions of mass (MM), length (LL), time (TT), and current (II), the dimensional formulas for each quantity are:

[ε0]=M−1L−3T4I2[\varepsilon_0] = M^{-1} L^{-3} T^{4} I^{2} [L]=L1[L] = L^{1} [ΔV]=ML2T−3I−1[\Delta V] = M L^{2} T^{-3} I^{-1} [Δt]=T1[\Delta t] = T^{1}

Step 3: Calculate the dimensional formula of XX.

Substitute the individual dimensions into the expression for XX.

[X]=[ε0][L][ΔV][1Δt][X] = [\varepsilon_0] [L] [\Delta V] \left[\frac{1}{\Delta t}\right] [X]=(M−1L−3T4I2)(L1)(ML2T−3I−1)(T−1)[X] = \left(M^{-1} L^{-3} T^{4} I^{2}\right) \left(L^{1}\right) \left(M L^{2} T^{-3} I^{-1}\right) \left(T^{-1}\right) [X]=M−1+1L−3+1+2T4−3−1I2−1[X] = M^{-1+1} L^{-3+1+2} T^{4-3-1} I^{2-1} [X]=M0L0T0I1[X] = M^{0} L^{0} T^{0} I^{1} [X]=I[X] = I

Step 4: Compare with the dimensions of the given options.

Analyze the dimensional formulas of the options:

[resistance]=ML2T−3I−2[\text{resistance}] = M L^{2} T^{-3} I^{-2} [charge]=IT[\text{charge}] = I T [voltage]=ML2T−3I−1[\text{voltage}] = M L^{2} T^{-3} I^{-1} [current]=I[\text{current}] = I

The dimensional formula of XX matches that of current.

Answer: Current

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