- •Ministry of education and science of ukraine
- •Module structure Module № 1. „ Electrical current and magnetic field of a current” – 72 hours total
- •List of laboratory works
- •Introduction
- •Далее Лаб 2.1 и 3.4
- •3.2. Work of electrostatic field forces
- •3.3. Field potential. Difference of potentials.
- •3.4. Graphical representation of electric field. Field lines and equipotential serfaces
- •3.5. Relation between intensity and potential
- •3.6. Vector of electric displacement
- •5. Data processing
- •6. Work execution order and experimental data analysis
- •7. Test questions
- •8. Content of the report
- •Laboratory work № 2-2
- •3.3. Kirchhoff’s rules
- •4.1. Condition of balance of bridge according to Ohm’s law
- •4.2. Condition of balance of bridge according to Kirchhoff rules
- •5. Data processing
- •6. Work execution order and experimental data analysis
- •7. Test questions
- •8. Content of the report
- •5) Equations for calculation:
- •7) Quantities calculation: …
- •3.1. Ohm’s law for various circuit units
- •4. Description of laboratory research facility and methodology of measurements
- •4.1. Measurement of emf of a source with the compensation method
- •4.2. Measurement of emf of a source by direct method
- •5. Data processing
- •6. Work execution order and experimental data analysis
- •5.1. Compensation method
- •5.2. Direct method
- •7. Test questions
- •8. Content of the report
- •7) Calculation of quantities:
- •7.1) Compensation method:
- •7.2) Direct measurement method:
- •Laboratory work № 2-4
- •3.2. Dependence of total power, useful power and efficiency of a source from the external load resistance. Maximal power theorem
- •3.3. Dependence of total power, useful power and efficiency of the source from a current
- •4. Description of laboratory research facility and methodology of measurements
- •5. Data processing
- •6. Work execution order and experimental data analysis
- •7. Test questions
- •8. Content of the report
- •7) Calculation of quantities:
- •Here, l – is the length of midline of a torus.
- •3.2. Earth’s magnetic field
- •4. Description of laboratory research facility and methodology of measurements
- •5. Data processing
- •6. Work execution order and experimental data analysis
- •7. Test questions
- •8. Content of the report
- •3.2. Magnetic Properties of different materials
- •Magnetic Properties of different materials
- •Diamagnetism
- •Paramagnetism
- •Ferromagnetism
- •Hysteresis
- •Hysteresis loop
- •4 Description of laboratory research facility and methodology of measurements
- •6) Table of measurements
- •7) Calculation of quantities and their errors
- •9) Final results :
- •10) Conclusions:
- •Bibliography
- •Physics
7) Calculation of quantities:
7.1) Compensation method:
Statistical absolute error:
.
Device error of voltmeter:
.
Total absolute error and relative error of in compensation method:
; .
7.2) Direct measurement method:
Relative error of direct measurement method:
; ;
; ;
; .
8) Final results: 8.1) Compensation method: x = (<x> x)VV; =… %.
8.1) Direct measurement method: Graph of dependence of β2DIR from r/RV : |
9) Conclusions: In compensation method … (ststistical or device) error make a main contribution to an absolute error. For a direct method the measuring we can consider correct in range where resistance of voltmeter … (more greater or more less), then internal resistance of source.
10) Data: “___” _____20___. Work done by: ______ Work checked by:
(Surname, readable)
Laboratory work № 2-4
1. Topic: POWER IN THE DIRECT CURRENT CIRCUIT
2. Goal of the work:
2.1. Study total power, useful power, and electrical efficiency dependence on current and external load resistance.
2.2. Finding the condition of matching of source to a circuit loading.
3. Main concepts
3.1. Types of power in a DC circuit
For direct current flowing in the circuit, there must be a source, where the extraneous forces create the excess of positive charges on one terminal of a device. Work of extraneous forces for moving the electric charge q between terminals inside the source, is equal (53):
АEXTR=q, (68)
where – EMF of the source.
As the result charges get potential energy, which is equal q. If we close the circuit this potential energy will change into kinetic energy of electric charge's motion and the current will flow. The kinetic energy of electric charges will change into a heat, if there are no other energy transformations (for example, into mechanical in electric motors etc.). According to the energy conservation law, this total energy, which is being dissipated along the whole circuit during a time interval t, is equal to work of extraneous forces for this time WT= АEXTR.
Therefore a total power РT, which is being dissipated in electric circuit, is equal to work of extraneous forces per unit time:
. (69)
Using (68) and definition of current (19), we obtain:
. (70)
Useful power PU is being dissipated in on the external part of the circuit R (heat, light, mechanical work, etc.):
, (71)
where UR – potential difference on the external part of the circuit R.
The power loss PL due to heating of the internal resistance of source r:
, (72)
where Ur – potential difference on the internal part of the circuit r.
By magnitude of efficiency we can estimate how the energy of the source is consumed. Efficiency of the source is the quantity, which is numerically equal to ratio of useful power PU due to total power РT:
=. (73)
If we take into account equations (70) and (71) we can write
=. (74)