View source for CircuitJS/C2/Kirchhoff's-Law/English


{| border="1"
|-
|| '''Visual Cue'''
|| '''Narration'''
|-
|| '''Slide:1'''
'''Title slide'''
|| Welcome to the Spoken tutorial on '''Kirchhoff's Law''' using '''Circuitjs''' simulator.
|- 
|| '''Slide 2:'''

'''Learning Objectives'''
|| In this tutorial, we will learn about,
* Kirchhoff’s Voltage Law and
* Kirchhoff’s Current Law.
|- 
|| '''Slide 3:'''

'''System Requirement'''
|| To record this tutorial, I am using:
* '''Ubuntu Linux '''20.04 OS
* '''CircuitJS '''Application

|- 
|| '''Slide 4:'''

'''Prerequisite'''
|| To follow this tutorial, you should have a basic knowledge of,
* Electrical circuits.

|- 
|| '''Slide 5:'''

'''Kirchhoff's Voltage Law'''

'''Voltage Law.png'''
|'''Kirchhoff'''’s '''Voltage''' Law states that,
* The sum of all voltages in a closed loop is zero.

Where I is the current flowing in the circuit.

Note : Voltage drops across resistors R1, R2 and R3 are calculated as I x R1, I x R2 and I x R3 respectively.
|- 
|| '''Slide 6:'''
'''Kirchhoff’s Current Law'''
Current Law.png
||'''Kirchhoff'''’s '''Current''' Law states that,
*The sum of currents entering the junction is equal to the sum of currents leaving the junction.

I<sub>1</sub> and I<sub>2</sub> are entering currents at the junction and I<sub>3</sub>, I<sub>4</sub> and I<sub>5</sub> are leaving currents.
|- 
|| 

'''Kirchhoff’s Law.png'''
|| Let’s make this complex circuit with 2 DC sources to verify '''Kirchhoff's Voltage and Current Law'''s.
|- 
|| 

|| For '''Kirchhoff'''’s Law circuit, we require,
* 5 resistors of 1 Kilo Ohms.
* 2 DC power supply of 5 Volts.

|- 
|| 

Point to the menu bar.

Click on '''File''' and select '''New Blank Circuit.'''

|| Let us open the '''circuitJS '''interface.

In the menu bar, click on '''File''' and select '''New Blank Circuit.'''
|- 
|| Click on the '''Draw''' option and select '''Add resistor.'''

Click and drag to draw a resistor.
|| Click on the '''Draw''' option and select '''Add resistor.'''

Click and drag to draw a resistor as shown.

By default, the value of this resistor is 1 Kilo Ohm.

|- 
|| Duplicate the resistor.

Right-click on the resistor, >> select the '''Duplicate '''option.

|| We need a total of 5 resistors of the same value for the circuit.

Right-click on the resistor, then select the '''Duplicate '''option.

This will generate a resistor of the same value.

Repeat this process until you have 5 resistors in the work area.

Connect and place all the resistors in the same way as shown here.

|- 
|| Use Add Text option for label


|| 

Use the '''Add Text''' option to give labels to these resistors.

Give labels as R1, R2, R3, R4, and R5 respectively as shown here.
|- 
|| 

Show the path to find the DC power supply

Click on '''Draw''', go to''' Inputs and Sources''', >> select '''Add Voltage Source (2-terminal).'''

|| Now we need two DC power supplies to power up the circuit.

Click on '''Draw''', go to''' Inputs and Sources''', and select '''Add Voltage Source (2-terminal).'''

Drag and draw the DC power supply in the work area.
|- 
|| 

Duplicate the DC power supply,

Right-click on the DC power supply, >> choose the '''Duplicate '''option.

|| Right-click on the DC power supply, and choose the '''Duplicate '''option.

Now you'll have two DC power supplies in the work area.

Arrange and place the DC power supplies in the circuit as shown here.
|- 
|| Name the power supplies 
|| Refer to the circuit diagram shown above to check the polarity of the DC power source.

Use the '''Add Text''' option to label these power supplies.

Name the power supplies as V1 and V2 as shown here.

|- 
|| 
|| For better understanding, we will denote a letter to each of the junctions in the circuit.

Use the '''Add Text''' option to denote a letter.

Name these junctions as A, B, C, D, F and G as shown.
|- 
|| Point to ABFG circuit
|| The circuit ABFG, consists of resistors R1, R5, R3 and power supply V1.

The current I<sub>1</sub> flows in a clockwise direction in this circuit.
|- 
|| Point to CBFD circuit
|| The circuit CBFD, consists of resistors R2, R5, R4 and power supply V2.

The current I<sub>2</sub> flows in an anti-clockwise direction in this circuit.

And, the current I<sub>3</sub> flows through R5 resistor.
|- 
|| point the cursor on the specific resistor

|| To find the characteristics, point the cursor on the specific resistor.

The resistor characteristics are shown at the bottom right corner.
|- 
|| '''Slide 7:'''

Kirchoff's law final slide.png
|| According to Kirchhoff's voltage law

For circuit ABFG, the equation is

V1 = I<sub>1</sub>R1 + I<sub>3</sub>R5 + I<sub>1</sub>R3

For circuit CBFD, the equation is

V2 = - (I<sub>2</sub>R2 + I<sub>3</sub>R5 + I<sub>2</sub>R4)

Since current I<sub>2</sub> flows in anti-clockwise direction, we have to assign a -(minus)sign in the equation.
|- 
|| 
|| Let us note down the current flowing through various resistors.

To find the value of I<sub>1</sub>, click on the R1 or R3 resistor.

We can see that the value of I<sub>1 </sub>is 1.25 milli-Ampere at the right bottom corner of the screen.
|- 
|| 
|| Likewise, click on the R2 or R4 resistors. 

The value of I<sub>2 </sub>is 1.25 milli-Ampere.

Similarly, to find the value of I<sub>3</sub>, click on the R5 resistor.

The value of I<sub>3 </sub>is 2.5 milli-Ampere.
|- 
|| 
||In this circuit, value of all resistors, that is, R1, R2, R3, R4, and R5 is 1 Kilo Ohm.
|- 
|| 
|| Now let us do the calculation and find the value of V1 and V2.

And also check if Kirchhoff's voltage law holds true for this circuit.
|- 
|| '''Slide 8:'''

'''Verification of Kirchhoff's voltage law '''

V1 = I<sub>1</sub>R1 + I<sub>3</sub>R5 + I<sub>1</sub>R3,

V1 = 1.25 + 2.5 + 1.25

<nowiki>= 5</nowiki>

V2 = - (I<sub>2</sub>R2 + I<sub>3</sub>R5 + I<sub>2</sub>R4)

V2 = -(1.25 + 2.5 + 1.25 )

<nowiki>= -5 </nowiki>

|| Verification of Kirchhoff's voltage law:

After substituting the above values, 

V1 is 5 volts
V2 is -5 volts 

Kirchhoff’s Voltage Law formula is:

V = V1 + V2
V = 5 + (- 5 ) ( Five plus minus of five)
V = 0

Here, the sum of all the voltages in the closed circuit is 0.

Hence Kirchhoff’s voltage law is verified.
|- 
|| '''Slide 9:'''

'''Verification of Kirchhoff’s Current Law'''
I<sub>1</sub> = 1.25mA
I<sub>2</sub> = 1.25mA
I<sub>3</sub> = 2.5mA

Image:

Kirchoffs law final slide.png
|| Verification of Kirchhoff’s Current Law:

Substitute the above values in the current law equation.

Kirchhoff’s Current Law formula is:

I<sub>1</sub> + I<sub>2</sub> = I<sub>3</sub>.

1.25mA + 1.25mA = 2.5mA


According to Kirchhoff’s current Law formula, at Junction B, current I1 and I2 enter and current I3 leaves. 

Similarly, at junction F, current I<sub>3</sub> enters, and I<sub>1</sub> and I<sub>2</sub> leave.

Thus Kirchhoff’s current law is verified.
|- 
|| 
|| This brings us to the end of the tutorial. Let us summarize.
|- 
|| Slide 10:

Summary 
|| In this tutorial, we learnt about
* Kirchhoff’s Voltage Law.
* Kirchhoff’s Current Law.

|- 
|| '''Slide 11:'''

'''Assignment 1'''
|| As an assignment,

* In the above circuit, change the value of V1 to 12V and value of R5 to 4 Kilo Ohms.
* Keep the values same for other components in the circuit.
* Verify Kirchhoff's Voltage and Current laws

|- 
|| '''Slide 12:'''

'''About Spoken Tutorial project'''
|| The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.
|- 
|| '''Slide 13&nbsp;:'''

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|| The&nbsp;'''Spoken Tutorial Project'''&nbsp;Team conducts workshops and gives certificates.

For more details, please write to us.
|- 
|| '''Slide 14: '''

'''Forum for specific questions'''
|| Please post your timed queries in this forum.
|- 
|| '''Slide 15:'''

'''Acknowledgement'''
|| Spoken Tutorial project was established by the Ministry of Education(MoE), Govt of India
|- 
|| '''Slide 16:'''

'''Thank you'''
|| This tutorial has been contributed by FOSSEE and Spoken Tutorial Project, IIT Bombay.

Thank you for watching.
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|}