# Homework Help: What is the resistance of the wire and its uncertainty?

1. Jun 10, 2008

### looi76

1. The problem statement, all variables and given/known data
An experiment is done to measure the resistance of a wire.
The current in the wire is $$1.0 \pm 0.2A$$ and the potential difference across the wire is $$8.0 \pm 0.4V$$.
What is the resistance of the wire and its uncertainty?

2. Relevant equations
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3. The attempt at a solution

$$\frac{0.2}{1.0} \times 100 = 20\%$$

$$\frac{0.4}{8.0} \times 100 = 5\%$$

Total Percentage Uncertainty = $$25\%$$

How can I get the uncertainty?

2. Jun 10, 2008

### seycyrus

Do you have a lab manual for your course? Sometimes they cover this in the introduction. Also, in this course, do they use calculus, or is it precalc?

3. Jun 10, 2008

### looi76

I don't think this question need calculus! It is a multiple choice question and the choices are:
(A) $$(8.0 \pm 0.2)\omega$$
(B) $$(8.0 \pm 0.6)\omega$$
(C) $$(8 \pm 1)\omega$$
(D) $$(8 \pm 2)\omega$$

4. Jun 10, 2008

### Reshma

$\omega$?...I think You mean $\Omega$. You have been given the Voltage (V) and the Current (I). Use Ohm's law R = V/I to find the resistance. You can't add the percentages like that. Hint: You have to include the tolerance value of the Current and voltage in the formula.

5. Jun 10, 2008

### Redbelly98

Staff Emeritus
Okay, which of those answers has a 25% uncertainty?