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Question

If a scientist is comparing the energy output of two light bulbs and records their values in joules, which dimensional formula should be used to represent energy in the SI system?

This question was previously asked in
RRB NTPC 2025 Under Graduate CBT 2 Question Paper PDF (17-Sep-2026) (Shift 1)
The correct answer is

\([M L^2 T^{-2}]\)

Energy is defined as the capacity to do work, and work is force multiplied by displacement.

Force has the dimensional formula \([M L T^{-2}]\), so work (and hence energy) is \([M L T^{-2}] \times [L] = [M L^2 T^{-2}]\).

This matches the joule, the SI unit of energy, confirming the dimensional formula is unique among the given options.

Hence, the correct dimensional formula for energy is \([M L^2 T^{-2}]\).

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