Name: measurement precision and significant figures
Uploaded: 2023-04-30T10:48:20.000Z
Duration: 1 min 44 s
Channel: JoVE

La certezza della misura dipende da due fattori: il numero di cifre nella misura e la precisione dello strumento utilizzato.
In una grandezza misurata, tutte le cifre, inclusa l'ultima cifra incerta, sono chiamate cifre significative e possono essere determinate utilizzando regole specifiche.
Tutte le cifre diverse da zero e tutti gli zeri vincolati, che si trovano tra due cifre diverse da zero, sono significativi. Ad esempio, 28 ha due cifre significative, mentre 26,25 ne ha quattro e 208 ne ha tre.
Gli zeri iniziali non sono mai significativi, poiché individuano solo il punto decimale. Ad esempio, 0,00208 ha tre cifre significative. Tali quantità possono essere espresse utilizzando notazioni esponenziali. Quindi, 0,00208 può essere scritto come 2,08 × 10−3.
Gli zeri finali sono significativi solo nei numeri in formato decimale. 2200 ha due zeri finali e due cifre significative, mentre 2200.0 e 2200.1 hanno entrambi 5 cifre significative.
Per le quantità senza punti decimali, il significato degli zeri finali diventa ambiguo. Pertanto, 2200 può essere scritto come 2,2 × 103 con due cifre significative o 2,20 x 103 con tre cifre significative.

regole per cifre significative

In ogni misura, la precisione dello strumento di misura usato è un fattore essenziale. Un ordinario righello, per esempio, può misurare la lunghezza del millimetro più vicino; d'altra parte, un calibro, può misurare la lunghezza al più vicino 0.01mm. Di conseguenza, il calibro è uno strumento di misura più preciso perché può misurare variazioni di lunghezza estremamente piccole. Le misurazioni sono più accurate se lo strumento di misura è più preciso.

Va sottolineato che quando rappresentiamo i valori misurati, l'ultima cifra digitata è stata calcolata in qualche modo dalla persona che ha effettuato la misurazione. Per esempio, una persona che misura la lunghezza di un bastone con un righello nota che sembra essere tra i 13,2cm e i 13,3cm, quindi deve stimare il valore dell'ultima cifra. La regola delle cifre significative ci dice che l'ultima cifra di una misurazione che viene annotata è la prima a presentare qualche incertezza. Inizia con il primo valore misurato a sinistra e conta il numero di cifre fino ad arrivare all'ultima scritta a destra per determinare il numero di cifre significative di un valore. Le cifre significative rappresentano la precisione dello strumento usato per misurare un certo valore.

Questo testo è adattato da <a href="https://openstax.org/books/university-physics-volume-1/pages/1-6-significant-figures">Openstax, University Physics Volume 1, Section: 1.6 Significant Figures.</a>

Regole per cifre significative

In qualsiasi misurazione, la precisione dello strumento di misura è un fattore essenziale. Un normale righello, ad esempio, può misurare la lunghezza al più vicino ...

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Rules for Significant Figures

measurement precision and significant figures

Measurement precision depends on the tool used, and significant figures show that precision. A ruler can measure length to the closest millimeter. A caliper can measure length to the nearest 0.01 mm, so it gives a more precise measurement because it can detect very small changes in length.

When a value is written from a measurement, the last digit is not exact. The person making the measurement must estimate that digit. For example, a stick that seems to fall between 13.2 cm and 13.3 cm must be recorded with a guessed last digit.

The last digit in a measurement is the first digit with some uncertainty. To find the number of significant figures, start with the first measured value on the left and count through the last digit written on the right. Significant figures show how precise the measuring tool was when the value was recorded.

Measurement Precision and Significant Figures

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rules for significant figures

Measurement precision depends on the tool used, and significant figures show that precision. A ruler can measure length to the closest millimeter. A caliper can measure length to the nearest 0.01 mm, so it gives a more precise measurement because it can detect very small changes in length. When a value is written from a measurement, the last digit is not exact. The person making the measurement must estimate that digit. For example, a stick that seems to fall between 13.2 cm and 13.3 cm must...

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Learn how ruler and caliper precision affects measurements and how to count significant figures from the first measured digit to the uncertain last digit.

Measurement Precision and Significant Figures | JoVE K12

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Measurement Precision and Significant Figures

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