What are the characteristics associated with a practical voltage source:
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Answer: B. terminal voltage cannot be higher than source e.m.f.
Explanation
Every practical voltage source possesses an internal electrical resistance that cannot be completely eliminated in reality. When current flows through the circuit, internal resistance causes an internal voltage drop according to Ohm's law. Subtracting this internal voltage drop from the source electromotive force yields a terminal voltage lower than the open-circuit emf. Ideal voltage sources maintain a constant potential difference regardless of the amount of current drawn by the load. Practical sources always exhibit voltage sag under heavy load conditions due to non-zero internal resistance. Terminal voltage equals open circuit emf only when zero current flows through the external circuit load.
Option a is less precise because terminal voltage can occasionally equal source emf when no load current flows. Option c is incorrect because internal resistance always causes a voltage drop whenever current is actively flowing. Option d is incorrect because practical voltage sources definitely exhibit measurable differences between emf and terminal voltage.
- Subject
- Engineering
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- Electrical Engineering
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- —
- Difficulty
- medium
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