Question

Which of the following cannot be measured:

• A. Resistance
• B. Voltage
• C. Voltage difference
• D. Displacement current

Hint:

Voltmeters always measure {potential difference}, never the absolute electric potential at a single point.

Answer 1

The Correct Option is B

Concept:
Only potential difference
between two points can be measured. Absolute electric potential (often loosely called “voltage” at a point) has no physical meaning unless a reference is specified.
Step 1: Analyze Each Option
(1) Resistance:
Resistance can be directly measured using an ohmmeter. \(\Rightarrow\) Measurable
(2) Voltage:
Voltage at a single point (absolute potential) cannot be measured because potential is defined relative to a reference level. \(\Rightarrow\) Not measurable
(3) Voltage difference:
Potential difference between two points can be measured using a voltmeter. \(\Rightarrow\) Measurable
(4) Displacement current:
Displacement current is measurable indirectly through its magnetic effects (as in Maxwell’s equations). \(\Rightarrow\) Measurable

Final Conclusion:
Only absolute voltage
(electric potential at a point) cannot be measured.