∑Vsupply = ∑Vdrop
VA + VB + VC + VD = 0
Starting at any point in the loop continue in the same direction noting the direction of all the voltage drops, either positive or negative, and returning back to the same starting point. It is important to maintain the same direction either clockwise or anti-clockwise or the final voltage sum will not be equal to zero. We can use Kirchoff's voltage law when analyzing series circuits.
Basic procedure to apply KVL and KCL :
1. Assume all voltages and resistances are given.
2. Label each branch with a branch current.
3. Find Kirchoff's first law equations for each node.
4. Find Kirchoff's second law equations for each of the independent loops of the circuit.
5. Use Linear simultaneous equations as required to find the unknown currents.
Objectives
1. To familiarize with computer simulation software (Multisim).
2. To show the application of Kirchhoff’s Voltage Law & Kirchhoff’s Current Law in series, parallel and combination circuits.
Equipments and Components
1. Digital/Analog Multimeter.
2. 4 resistors with different values (100 Ω, 1kΩ, 2kΩ and 4.7kΩ).
3. Logic trainer.
4. Multisim software.
Procedure
Part A
1. R1 = 1kΩ and R 2= 4.7kΩ resistor was selected and identified using colour code or multimeter.
2. Series circuit was patched same as the Diagram 1.
3. Positive voltage control was set to 10 V.
4. The voltage drop across R1 and R 2 was measured using voltmeter by setting it parallel to the resistor.
5. The above step was repeated using R1 = 100 Ω and R 2 = 2kΩ and the reading was recorded.
6. Results from experiments was compared with the simulation result.
Diagram 1
Results from experiment:
Set 1:
Set 2:
Comment: For set 1 ,the total voltage drop of a circuit which is VR1 , 1.75 v and VR2 , 8.25 v is
10.0 v .So, its not accomplished to KVL.This is because,the the total voltage drop is
Not equal to voltage source,10.02 v.Meanwhile,for set 2,same like set 1 the total
voltage drop of of a circuit which is VR1 , 0.47 v and VR2 , 9.52v is 9.99 v .
So, its not accomplished to KVL.This is because,the the total voltage drop not equal
to voltage source,10.02 v.
Results from simulation:
Set 1:
Set 2:
Comment: For set 1 ,the total voltage drop of a circuit which is VR1 , 1.75 v and VR2 , 8.25 v is
10.0 v .So, its not accomplished to KVL.This is because,the the total voltage drop is
Not equal to voltage source,10.02 v.Meanwhile,for set 2,same like set 1 the total
voltage drop of of a circuit which is VR1 , 0.47 v and VR2 , 9.52v is 9.99 v .
So, its not accomplished to KVL.This is because,the the total voltage drop not equal
to voltage source,10.02 v.
Part B
2. Parallel circuit was patched same as the Diagram 2.
3. Positive voltage control was set to 10 V.
4. The current drop across R1 and R 2 was measured using voltmeter by setting it series to the resistor and labeled IR1 and IR 2.
5. The above step was repeated using R1 = 100 Ω and R 2 = 2kΩ and the reading was recorded.
6. Results from experiments was compared with the simulation result.
Results from experiment:
Set 1:
Set 2:
Comment: For set 1 ,the result is IR1 is 10mA and IR2 2.2mA. The total current is 12.2m A.So,its
accomplished to the KCL,which is total current in is equal to current out.Meanwhile,
for set 2,the results for IR1 is 0.1A and IR2 0.48mA.The total current is 100.48mA.
So,its not accomplished to the KCL.This is because current in is not equal to current
Out.
Results from simulation:
Set 1:
Set 2:
Comment: : For set 1 ,the result is IR1 is 10mA and IR2 2.126mAThe total current is 12.126m
A.So,its not accomplished to the KCL,which is total current in is not equal to current
out.Meanwhile, for set 2,the results for IR1 is 0.1A and IR2 5.0mA.The total current
is 105.00mA.So,its not accomplished to the KCL.This is because current in is not
equal to current out.
Part C
1. R1 = 1kΩ , R 2= 4.7kΩ , R 3 = 100 Ω and R 4 = 2kΩ resistor was selected and identified using colour code or multimeter.
2. Series and parallel circuit was patched same as the Diagram 3.
3. Positive voltage control was set to 10 V.
4. The voltage drop and current drop across each resistor was measured using multimeter simultaneously.
5. The data is recorded and ws compared with the simulation’s data.
Diagram 3
Results from experiment:
Comment: All the value of result in the experiment was awfully close to the theoretical value and therefore, in this part of the experiment it shows that the KVL and KCL are true and can be applied.
Results from simulation:
Comment: All the value of result in the experiment was awfully close to the theoretical value and therefore, in this part of the experiment it shows that the KVL and KCL are true and can be applied.
Discussion
-
From experiment Part A,B,and C we had Vsupply = 10.02 V .An error was occurred because Vsupplys should 10.0 v.This is because the instrumental error was occurred.So,to overcome this problem,the students should be able use the instrument correctly and the technician should keep instrument optimized.When we doing practical for part A ,we\does not have many problem ,this because the objective for this experiment we have absolutely achieve . But absolute error was occurred.For the example,experiment A set 1 an absolute error was occurred,Absolute error is different between the expected value and the measured value.
e= Yn- Xn where e=absolute error
Yn= expected value
Xn=measured value
e=10.02-10.0
=0.02v
Error in percentage:
% error= e/Yn (100) = 0.02/10.02 (100) = 1.99%
2.Beside that, when we run our experiment, we always have different thinking to get better result.Thus, the gross error was occurred. Example, we have incorrect reading when we measured the multimeter. Also, parallax error should be taken into consideration. Parallax error is the error that human make when taking a reading from any device where our eyes are not perpendicular to the scale reading. To overcome this problem, we carefully read the scale reading to minimize any fault.
3.Next, the problem that our group have come to face is incorrect reading of the multimeter, voltmeter and ammeter. We suspected that the fault was caused by the instrument itself. To overcome this problem, we take at least three separate reading to obtain better reading.
Conclusion
From the experiment that we had conducted, we had practically use Kirchoff Law to determine the voltage drop, voltage supplied, current for each resistor in series and parallel circuit.
References