3. A thin wire was wound 30 times tightly over a boiling tube. The total length of the windings was found to be [tex]0.3 \text{ mm}[/tex]. Calculate the radius of the wire.



Answer :

Certainly! Let's break down the problem step-by-step to determine the radius of the wire, given that the thin wire was wound 30 times around a boiling tube, with a total length of 0.3 mm.

### Step-by-Step Solution:

1. Understand the Problem:
- You have a thin wire wound 30 times around a tube.
- The total length of the wire is 0.3 mm.
- You need to find the radius of the wire.

2. Establish Known Values:
- Total length of the wire (L) = 0.3 mm
- Number of windings (N) = 30

3. Determine the relationship between the total length and the circumference:
- When a wire is wound in a circular way, the total length of the wire is the sum of the circumference of all windings.
- The circumference of one winding is given by [tex]\( 2 \pi r \)[/tex], where [tex]\( r \)[/tex] is the radius of one winding.

4. Form the Equation:
- The total length of the wire is the product of the number of windings and the circumference of one winding:
[tex]\[ L = N \cdot (2 \pi r) \][/tex]
Therefore:
[tex]\[ 0.3 \, \text{mm} = 30 \cdot (2 \pi r) \][/tex]

5. Solve for the Radius (r):
[tex]\[ 0.3 = 30 \cdot 2 \pi r \][/tex]
[tex]\[ 0.3 = 60 \pi r \][/tex]
[tex]\[ r = \frac{0.3}{60 \pi} \][/tex]

6. Calculate the Value of the Radius:
Now, using the constant value of [tex]\( \pi \approx 3.14159 \)[/tex]:
[tex]\[ r = \frac{0.3}{60 \pi} \approx \frac{0.3}{188.495} \][/tex]
[tex]\[ r \approx 0.00159154943 \, \text{mm} \][/tex]

### Conclusion:
Thus, the radius of the wire is approximately 0.00159154943 mm.

This step-by-step process aligns with the methodology needed to solve the problem and finds the radius of the wire correctly.