Question:
Which one of the following is not a measurable quantity?
Which one of the following is not a measurable quantity?
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Displacement current is a mathematical concept ensuring continuity of current—it is not associated with real charge flow.
Updated On: Feb 4, 2026
- Voltage difference
- Voltage
- Resistance
- Displacement current
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The Correct Option is D
Solution and Explanation
Concept:
A measurable quantity is one that can be directly or indirectly measured using instruments.
In electromagnetism, some quantities are theoretical constructs introduced for
consistency of laws but are not directly measurable.
Step 1: Examine each option
Voltage difference: Measured directly using a voltmeter. \(\checkmark\)
Voltage: Defined as potential difference; measurable using standard electrical instruments. \(\checkmark\)
Resistance: Measured using an ohmmeter or calculated using \(V=IR\). \(\checkmark\)
Displacement current: Introduced by Maxwell to modify Ampère’s law. It does not correspond to actual flow of charge and cannot be measured directly. \(\times\)
Final Answer: \[ \boxed{\text{Displacement current}} \]
Step 1: Examine each option
Voltage difference: Measured directly using a voltmeter. \(\checkmark\)
Voltage: Defined as potential difference; measurable using standard electrical instruments. \(\checkmark\)
Resistance: Measured using an ohmmeter or calculated using \(V=IR\). \(\checkmark\)
Displacement current: Introduced by Maxwell to modify Ampère’s law. It does not correspond to actual flow of charge and cannot be measured directly. \(\times\)
Final Answer: \[ \boxed{\text{Displacement current}} \]
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