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An ideal ammeter and an ideal voltmeter has resistance ________ Ω and ________ respectively.

Asked in GUJCET 2024 · Conversion to ammeter and voltmeter

• (1) (∞, 0)
• (2) (0, 0)
• (3) (∞, ∞)
• (4) (0, ∞)

Step-by-step solution

Why the other options are wrong

• (1) The two are swapped. An ammeter is joined in series, so any resistance of its own would cut down the current it is meant to read: it must be 0. A voltmeter is joined in parallel, so it must be ∞.
• (2) The ammeter is right at 0, the voltmeter is not: a voltmeter of zero resistance would short out the element it is placed across, leaving no potential difference to measure.
• (3) The voltmeter is right at ∞, the ammeter is not: an ammeter of infinite resistance would block the very current it is meant to read.

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