JEE Main · 2026 · 28 Jan 2026 · Shift 2 · EM Waves

Which one of the following is not a measurable quantity?

(A)Voltage difference
(B)Resistance
(C)Voltage✓ Correct
(D)Displacement current

Answer: (C)

Solution

Electric potential is defined only with respect to a chosen reference, so the absolute potential, or voltage, at a single point has no directly measurable value. What an instrument actually measures is the potential difference between two points. Resistance and displacement current can also be determined from measurements, but the absolute voltage at a point cannot. Hence the quantity that is not measurable is voltage.

JEE Main · 2026 · 28 Jan 2026 · Shift 2 · Single correct option

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