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Capacitor question

2025 · 22 Jan · Shift 2 · Q54
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  5. /2025 · 22 Jan · Shift 2 · Q54

Capacitor question

2025 · 22 Jan · Shift 2 · Q54

JEE MainPhysicsCapacitorMCQ+4 / −1
Which one of the following is the correct dimensional formula for the capacitance in F ? M,L,T\mathrm{M}, \mathrm{L}, \mathrm{T}M,L,T and CCC stand for unit of mass, length, time and charge,
  1. A
    [F]=[CM−1 L−2 T2][\mathrm{F}]=\left[\mathrm{CM}^{-1} \mathrm{~L}^{-2} \mathrm{~T}^2\right][F]=[CM−1 L−2 T2]
  2. B
    [F]=[C2M−2 L2 T2][\mathrm{F}]=\left[\mathrm{C}^2 \mathrm{M}^{-2} \mathrm{~L}^2 \mathrm{~T}^2\right][F]=[C2M−2 L2 T2]
  3. C
    [F]=[C2M−1 L−2 T2][\mathrm{F}]=\left[\mathrm{C}^2 \mathrm{M}^{-1} \mathrm{~L}^{-2} \mathrm{~T}^2\right][F]=[C2M−1 L−2 T2]
  4. D
    [F]=[CM−2 L−2 T−2][\mathrm{F}]=\left[\mathrm{CM}^{-2} \mathrm{~L}^{-2} \mathrm{~T}^{-2}\right][F]=[CM−2 L−2 T−2]
View written solutionFree

Correct answer: C

  1. Use the definition of capacitance

Capacitance is defined as

Cap=QVC_{\text{ap}}=\frac{Q}{V}Cap​=VQ​

where QQQ is charge and VVV is potential difference.

So, dimensionally,

[capacitance]=[Q][V][\text{capacitance}] = \frac{[Q]}{[V]}[capacitance]=[V][Q]​
  1. Find the dimensional formula of potential

Potential difference is

V=workchargeV = \frac{\text{work}}{\text{charge}}V=chargework​

Now,

[work]=[force][distance]=[MLT−2][L]=[ML2T−2][\text{work}] = [\text{force}][\text{distance}] = [MLT^{-2}][L] = [ML^2T^{-2}][work]=[force][distance]=[MLT−2][L]=[ML2T−2]

Hence,

[V]=[ML2T−2][C][V] = \frac{[ML^2T^{-2}]}{[C]}[V]=[C][ML2T−2]​
  1. Now find capacitance dimension
[F]=[C][V]=[C][ML2T−2/C][F] = \frac{[C]}{[V]} = \frac{[C]}{[ML^2T^{-2}/C]}[F]=[V][C]​=[ML2T−2/C][C]​ [F]=[C]⋅[C][ML2T−2][F] = [C]\cdot \frac{[C]}{[ML^2T^{-2}]}[F]=[C]⋅[ML2T−2][C]​ [F]=[C2M−1L−2T2][F] = [C^2M^{-1}L^{-2}T^2][F]=[C2M−1L−2T2]
  1. Compare with options
  • A: [CM−1L−2T2][CM^{-1}L^{-2}T^2][CM−1L−2T2] ❌
  • B: [C2M−2L2T2][C^2M^{-2}L^2T^2][C2M−2L2T2] ❌
  • C: [C2M−1L−2T2][C^2M^{-1}L^{-2}T^2][C2M−1L−2T2] ✅
  • D: [CM−2L−2T−2][CM^{-2}L^{-2}T^{-2}][CM−2L−2T−2] ❌

Therefore, the correct option is:

C\boxed{\text{C}}C​
  1. Comparison with stored answer

Stored correct answer: C

My derived answer: C

So, the answers agree.

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