- #1
Skalvig
- 1
- 0
- Homework Statement
- Solve for the current
- Relevant Equations
- U = RI
This is the solution from the book. But I only get 0,037 A. What am I doing wrong?
In my book ##\frac {5.0}{2.67}## should be greater than 1. So both your answer and the book answer are wrong!Skalvig said:Homework Statement:: Solve for the current
Relevant Equations:: U = RI
View attachment 314307
This is the solution from the book. But I only get 0,037 A. What am I doing wrong?
##2\cdot 67##, not ##2.67##.Steve4Physics said:In my book ##\frac {5.0}{2.67}## should be greater than 1. So both your answer and the book answer are wrong!
Aha. Should have gone to Specsavers (for anyone in the UK).Orodruin said:##2\cdot 67##, not ##2.67##.
That one’s international I think.Steve4Physics said:Should have gone to Specsavers (for anyone in the UK)
Also, I'm assuming that ##2## is an exact number here. Again the rule that applies is:https://en.wikipedia.org/wiki/Significant_figures#Multiplication_and_division said:the calculated result should have as many significant figures as the least number of significant figures among the measured quantities used in the calculation.
Therefore the calculated result should have 2 significant figures; which both your answer and the book's answer have.https://en.wikipedia.org/wiki/Significant_figures#Identifying_significant_figures said:
- An exact number has an infinite number of significant figures.
- If the number of apples in a bag is 4 (exact number), then this number is 4.0000... (with infinite trailing zeros to the right of the decimal point). As a result, 4 does not impact the number of significant figures or digits in the result of calculations with it.
jack action said:The rule with multiplication/division:
Also, I'm assuming that ##2## is an exact number here. Again the rule that applies is:
Therefore the calculated result should have 2 significant figures; which both your answer and the book's answer have.
Somehow the book has rounded the answer to 1 significant figure (as if ##2## wasn't exact) but still added a trailing zero, which makes no sense.
I prefer your answer.
While this is likely, we simply don’t know this without knowing the original problem statement.hutchphd said:The book is incorrect. Their answer advertises itself to be correct to two sig fig but it is not.
I don't see a reasonable scenario where the book can be correct. Please elucidate.Orodruin said:While this is likely, we simply don’t know this without knowing the original problem statement.
hutchphd said:I don't see a reasonable scenario where the book can be correct. Please elucidate.
Orodruin said:Alternatively this is a middle step where some things were rounded but all decimals kept in the actual computation.
It is a stretch, but the intermediate rounding theory just barely holds water.Orodruin said:The book’s answer seems rounded without taking the last digit away. Alternatively this is a middle step where some things were rounded but all decimals kept in the actual computation.
Significant figures are the digits in a number that represent the accuracy or precision of the measurement. They are the reliable digits in a number and are used to indicate the level of uncertainty in a measurement.
The rules for determining the number of significant figures in a number are as follows:
- All non-zero digits are significant.
- Zeros between non-zero digits are significant.
- Zeros at the beginning of a number are not significant.
- Zeros at the end of a number with a decimal point are significant.
- Zeros at the end of a number without a decimal point are not significant.
Rounding to significant figures is important because it helps to maintain the accuracy and precision of a measurement. It ensures that the final result is not more precise than the original measurements used to calculate it.
The general rule for rounding to significant figures is to round the number to the nearest value with the desired number of significant figures. If the first digit to be dropped is 5 or greater, the last digit to be kept is increased by 1. If the first digit to be dropped is less than 5, the last digit to be kept remains the same.
Sure, let's say we have a measurement of 23.456 cm and we want to round it to 3 significant figures. The third digit is 4, so we leave it as it is. The fourth digit is 5, so we round up the third digit to 6. The final result is 23.5 cm, rounded to 3 significant figures.