View source for PhET-Simulations-for-Chemistry/C2/Conductivity/English

 '''Conductivity'''


'''Author: Vidhi Thakur'''


'''Keywords: PhET simulation,''' '''Conductivity, battery, metals, plastic, photoconductor, valence band, conduction band, band gap, spoken tutorial, video tutorial.'''

{|border=1
||'''Visual Cue'''
||'''Narration'''
|-
|'''Slide Number 1'''

'''Title Slide'''
||Welcome to this spoken tutorial on '''Conductivity.'''
|-
||'''Slide Number 2'''

'''Learning Objectives'''

||In this tutorial, we will learn how,

* Change in voltage makes the electrons move in the circuit.

* Large band gap in plastics do not allow conductivity.

* Shining light on a photoconductor causes it to conduct electricity.
|-
||'''Slide Number 3'''

'''System Requirement'''
||Here I am using

*'''Windows 11 (64 bit)'''.
*'''Java Version 1.8'''.

|-
||'''Slide Number 4'''

'''Pre-requisites'''


'''https://spoken-tutorial.org'''
|| To follow this tutorial, learner should be familiar with topics in High School Science.


Please use the link below to access the tutorials on '''PhET simulations.'''
|-
|| '''Slide Number 5'''

'''Link for PhET simulation'''

Point to
'''https://phet.colorado.edu/en/simulations/conductivity/about'''
|| Please use the given link to download the '''PhET simulation'''.


'''https://phet.colorado.edu/en/simulations/conductivity/about'''

|- 
|| '''Point to the file in the Downloads folder'''.
|| I have downloaded the '''Conductivity simulation '''to my '''Downloads''' folder.
|- 
|| '''Double click the file to open'''
|| To open the simulation, double-click on the file.

|- 
|| '''Cursor on the interface.'''
|| This is the interface of '''Conductivity simulation.'''
|-
|| Cursor on main panel.


Cursor on input box.




Cursor on electrons.




Cursor on the block.


|| The main panel consists of a circuit.

The circuit has a battery with a box to input the voltage.


Electrons represented as blue spheres are seen throughout the circuit.


A block of material is attached to the circuit at the bottom of the simulation.
|-
|| Cursor on left panel.

Point to the two bands.


Point to the lower band.


Point to the higher band.


Point to the gap.

|| The expanded rectangle is divided into two bands.


Low energy band is valence band and high energy band is conduction band.


The material conducts electricity when electrons are present in the conduction band.


The gap between the two bands is known as bandgap.

|-
||Point to the lower band.
||We can see that by default all electrons are in the low energy state.

|-
|| Cursor on '''Materials''' panel on the right.
Point one by one.


Cursor on shine the light checkbox.

|| On the right panel we can see the '''Materials''' section.


It has '''Metal, Plastic''' and '''Photoconductor''' radio buttons.


On the right panel the '''Shine the light'''  option is available.

|-
|| Cursor on torch.

|| At the bottom, we have a torch to shine light.

|-
|| 



Click on up arrow on battery voltage box till 0.2 volts.


|| Let us leave the default selection of material as '''Metal'''. 


Click the up arrow in the '''Battery Voltage''' box to increase the voltage to 0.2 volts.

|-
||Point to the circuit.
||Observe the movement of electrons in the circuit.


It means current is flowing through the circuit.
|-
||Point to the valence band in the left panel.
||Observe the movement of electrons in the valence band.

|-
|| Click on the Pause button.
|| Let us now pause the simulation.
|-
|| 




Point to the circuit.

Point to the circuit.
|| This simulation helps to understand the concept of conductivity.


Observe that electrons are present in the circuit, but are not moving.

|-
||Click the '''Play''' button at the bottom.
||Now click the '''Play''' button.

|-
||Only narration
||The electrons start moving, as we increase the voltage.

|-
|| Click the up arrow button of Battery Voltage to 2 V.
|| Let's increase the voltage to 2 volts and observe.

|-
||

Point to the circuit.


||As voltage increases the potential difference between the terminals increases.


The electrons now move faster and also move to higher energy levels.
|-
|| Only narration.
||This makes metals good conductors of electricity.
|-
|| Click on the '''Plastic''' radio button.




Point to band gap in the left panel.
|| Let us change the material to '''Plastic'''.


Observe that the energy gap between the two bands has increased.

|-
||Point to the circuit and to Voltage box: 2 V.
||We do not see the movement of electrons, even at high voltage. 

|-
||Click the '''Shine The Light '''checkbox.


||Now let us click the '''Shine The Light '''checkbox.


Observe that even after shining light electrons are not moving.

|-
|| Cursor on left panel >> band gap.







|| The band gap for '''plastic''' is very high.


So current does not flow in the circuit even after shining the light.


Hence '''plastic''' is a non-conductor.
|-
|| Uncheck the '''Shine The Light''' check box.
|| Let us uncheck the '''Shine The Light''' check box.

|-
|| Click on the '''Photoconductor''' radio button.
|| Let us change the material to '''Photoconductor'''.

|-
||Point to Voltage box: 2 V.
||Even at high voltage no movement of electrons is seen. 

|-
||Click the '''Shine The Light''' check box.


Point to the movement of electrons.



||Let us shine the light now.


We can now see the movement of electrons as light strikes the '''photoconductor'''.

|-
||Point to the electrons in the energy bands in the left panel.
||Observe that some electrons excite to the higher energy band.

|-
|| Cursor on Left panel.
|| Band gap for a '''photoconductor''' is less than '''plastic''' and more than metal.


Hence when light strikes the material it excites electrons to high energy levels.

|-
||Only narration
||This intermediate material is a semiconductor with a small band gap.


Semiconductors conduct electricity in the presence of light, heat and impurities.
|-
|| 
|| With this we come to the end of this tutorial.

Let's summarise.
|-
|| '''Slide Number 6'''

'''Summary'''
|| In this tutorial we have learnt how,

*Change in voltage makes the electrons move in the circuit.
*Large band gap in '''plastics''' do not allow conductivity.
*Shining light on a '''photoconductor''' causes it to conduct electricity.

|-
|| '''Slide Number 7'''

'''Assignment'''
| Here is an assignment for you.

Check if,
*The conductivity of a metal changes when light is shined.
*Photoconductors conduct electricity when battery voltage is decreased.

|-
|| '''Slide Number 8'''

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


Please download and watch it. 
|-
|| '''Slide Number 9'''

'''Spoken tutorial workshops '''
|| We conduct workshops using spoken tutorials and give certificates. 


For more details, please contact us. 
|-
|| '''Slide Number 10'''

'''Answers for THIS Spoken Tutorial '''
|| Please post your timed queries in this forum.
|-
|| '''Slide Number 11'''

'''Acknowledgement '''
|| Spoken Tutorial project is funded by the Ministry of Education (MoE), Govt. of India 
|-
|| 
|| This is Vidhi Thakur, a FOSSEE summer fellow 2022, IIT Bombay signing off.

Thank you for joining.

|-
|}