II. Objectives: To study the application of Kirchhoff’s Law to a D.C. network by comparing the observed and the computed values of the currents in the circuit.
III. Apparatus: Resistance Module, 1pc. Battery of two cells (3 volts), 1pc. Dry cell (1.5 volts), Multitester, 4 pairs connectors
IV. Procedure with Experimental Setup:
Part A. 1.) The apparatus was arranged as in diagram 1. The switches were left open until it is checked. 2.) With the switches closed the voltages V1 and V2 across the batteries were measured with a voltmeter. 3.) Considering V1, V2, R1, R2 and R3 as known, the Kirchhoff’s law was applied to the circuits and the correct number of independent current and voltage equations necessary to solve for the unknown current in each branch was written, that is one current equation and the fewest number of voltage equations that will include every emf and every resistance at least once in a set of equations. The equations for these currents were solved. 4.) Having calculated the current in each brach by an application of Kirchhoff’s Laws, the respective currents were measured experimentally. The circuit was break in turn in each branch and the ammeter was inserted in series to observe the values of the currents. 5.) The percentage error between the observed values of the currents and those computed by Kirchhoff’s Laws were calculated.
Part B. 1.) The series of observation and calculations were repeated using the arrangement in figure 2.
V. Tabulated Data and Results
Part A.
R1=2.6 Ω
R2=3.0 Ω
R3=3.3 Ω
V1=1.373 V
V2=2.648 V
Resistors | I (comp.) | I (obs.) | Deviation | % Error | R1 | 3.368 mA | 3.4 mA | 99.6 | 1 | R2 | 422.081 mA | 425 mA | 49.996 | 0.7 | R3 | 418.714 mA | 418.6 mA | 50.395 | 0.3 |
Part B.
R4=11.2 Ω
V1=1.373 V
V2=2.648 V
Resistors | I (comp.) | I (obs.) | Deviation | % Error | R1 | 0.263 | 0.27 | 70.968 | 3 | R2 |