Circuit Analysis and Equivalent Circuit Determination · RMPH 2014 #2
Physics · electromagnetism
Problem
This experimental problem proposes an analysis for an electrical black box, which has three terminals - denoted by 1,2,3. To discover the elements that compose it, it is provided a measuring device comprising a voltage source variable (denoted by S), connected in series with an ammeter (denoted by A); the two terminals of the device are denoted by P and Q. To the same terminals P and Q is mounted a voltmeter (denoted by V). Ammeter and power supply have negligible internal resistance; internal resistance of the voltmeter can be considered as being infinite.
The experimental data from three different terminal configurations are:
Table 1 (terminals 1,2,P connected; terminals 3,Q connected):
| U(V) | -6 | -4 | -2 | 0 | 2 | 4 |
| I(A) | -0.2 | 1.2 | 2.6 | 4.0 | 5.4 | 6.8 |
Table 2 (terminals 2,3,P connected; terminals 1,Q connected):
| U(V) | 0 | 2 | 4 | 6 | 8 | 10 |
| I(A) | -5.2 | -4.0 | -2.8 | -1.6 | -0.4 | +0.8 |
Table 3 (terminals 3,1,P connected; terminals 2,Q connected):
| U(V) | -6 | -4 | -2 | 0 | 2 |
| I(A) | -0.6 | 0 | 0.6 | 1.2 | 1.8 |
Assume that all current-voltage dependencies are linear.
Task 2
2.a. Determine the values of the electrical resistance of the resistors and electromotive force (emf) of ideal voltage sources that form the simplest circuit (a circuit triangle, delta, Δ), which has the behavior described by the above data. Keep in mind that the ideal voltage source connected in series with the resistor having the lowest electrical resistance, has an emf of 10V.
2.b. Draw the equivalent circuit diagram for black box. Write on diagram the values of electrical resistance and emf of the sources - as they results in the task 2.a.