Difference between revisions of "PhET-Simulations-for-Chemistry/C2/Conductivity/English"

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* The conductivity of a metal changes when light is shined.
 
* The conductivity of a metal changes when light is shined.
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* Photoconductors conduct electricity when battery voltage is decreased.
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* Photoconductors conduct electricity when voltage is decreased after shining the light.
  
 
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Latest revision as of 13:10, 23 January 2023

Conductivity


Author: Vidhi Thakur


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


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

PhET simulations

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 metal 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 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.

Only Narration 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 voltage is decreased after shining the light.
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

Acknowledgements

Spoken Tutorial project is funded by the Ministry of Education (MoE), Govt. of India
Slide Number 12

Thank you

This is Vidhi Thakur, a FOSSEE summer fellow 2022, IIT Bombay signing off.

Thank you for joining.

Contributors and Content Editors

Madhurig, Nancyvarkey, Vidhithakur

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