Page 28 - 6413

the current strength on the voltage according to Ohm's law is
performed).
2. Calculate the specific resistance of the conductor according to
the formula (37.8), substituting the experimental data relating to the

biggest length of the conductor. In this calculation, the relative error
will be the smallest.
3. Derive the formula of the relative error:

  U   d l  I 
   2   (37.9)
 U  d l I

Absolute errors of current І and voltage U are determined by
the accuracy classes of the corresponding electrical measuring devices.
Absolute error of length l = ± 0,5 mm is measured as half price of

the smallest division of the large-scale ruler. Absolute error of the
diameter of the wire is d = ± 0,05 mm is determined as the half price

of the smallest division of the caliper, which measures the diameter.
4. Calculate the relative error, after the relative one an absolute
error of the resistivity of the researched conductor.

5. Test questions.
1. Write down and explain Ohm's law for a homogeneous circle.
What units is the resistance of a conductor measured in?

2. How does the conductor's resistance depend on its length and
cross-sectional area?
3. Give the definition the resistivity of the conductor.

4. Write down and explain Ohm's law in a differential form.
5. What are the substantive provisions of the classical electronic
theory of conductivity of metals?

6. Outline Ohm's law in a differential form based on the classical
electronic theory of conductivity of metals.
7. What is the method of experimental verification of Ohm law
and the value of the resistivity of the conductor.

8. Output the formula of errors.

27