alleryStart learning →An ideal AMMETER has internal resistance
Ainfinite
Bexactly $1\Omega$
Cvery low (ideally zero)
Dequal to the circuit load
Answer & Solution
Correct answer: C. very low (ideally zero)
1. AMMETER measures CURRENT, connected IN SERIES with the circuit element.
2. To not disturb the current, the ammeter must add MINIMAL resistance — ideally ZERO.
3. CONTRAST with VOLTMETER (option A's case): a voltmeter is in PARALLEL with the element, and must have INFINITE resistance ideally so as not to draw any current.
4. Real ammeters have small but nonzero resistance, causing a slight 'burden voltage' that introduces measurement error.
5. Other options are not ideal characteristics.
_Source: Tony Kuphaldt, "Lessons in Electric Circuits — DC", Vol I, Ch 8 (Measurement instruments)._
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