Phys 102
Kikchoff’s Current and Loop Laws
Manju Sogi & Alma Fuentes
Abstract
This experiment will introduce Kirchhoff’s circuit laws and will be applied to elementary
multi-loop circuits, while comparing measured branch current with predicted currents.
Equipment
Breadboard
Resistor 10< R < 100 Ohms
Old fashioned ammeter
Batteries
Procedure
1. Choose three resistors and named them R1, R2, R3, record their values.
2. Build the following circuit.
3. Record the voltage across each circuit and current across each branch.
4. Build the circuit number 2.
5. Measure the voltage across each circuit and current in each branch.
Data
Circuit 1
Circuit 2
V1
V2
V3
Volts
0.369
6.44
5.58
Volts
1.89
0
4.98
I1
I2
I3
mAmps
1.98
7.9
9.9
mAmps
5.98
0
5.98
Ohms
180
820
560
Ohms
180
120
560
820
R1
R2
R3
R4
Calculations
Circuit 1
Theoretical
I1= I2+I3
V1-I1R1-I2R2-V2-V3=0
V3+V2+I2R2-I3R3=0
mAmps
I1=2.2
I2 = -7.8
I3 = 10
Circuit 2
I2 = 0
I1= I3
V1-R1I1-I1R4-V2-V3=0
6-180I1-I1820-3-9=0
I1= 6 mAmps
I3= 6 mAmps
I2 = 0 mAmps
Error Analysis
The purpose of this lab was to obtain results for inaccurate equipment and make
conclusions based on those measurements.
The use of the old fashioned ammeter is difficult to use and therefore causing errors to be
taken account.
The use of the breadboard and wires also contain errors that need to be taken into
account.
% Error = [Theoretical – Experimental] X (100)
Theoretical
Circuit 1
I 1 % Error = 2.2-1.98 X 100 = 10 %
2.2
I2 = 1.28%
I3 = 1.01 %
Circuit 2
I 1 % Error = 6-5.98 X 100
6
= .33 %
I2 = 0 %
I3 = .33%
Conclusion
In this experiment, we learned to apply Kirchhoff’s circuit laws to some elementary types
of multi-loop circuits, as well as comparing our measured branch currents with the
theoretical. Per data and after doing calculations we had .33% error in the second circuit
for the first current and the third current which was a small error percentage. However for
the second current we had a 0% error because our measured current was the same as the
theoretical. The error percentage could be attributed that the positive and negative wires
had a small give or take amount within the bread board circuit thus our data had a
percentage error. Furthermore, error in data could’ve been due to flaws in equipment or
inaccuracy due to human error while reading the voltmeter. In theory, we should’ve
measured the theoretical values as stated above but weren’t able to achieve due to error
possibilities in equipment or the human eye as mentioned above.
Grade = 100