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.

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.	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. We can see that by default all electrons are in the low energy state.
Cursor on Materials. Cursor on shine the light.	On the right panel we can see the Materials section. It has Metal, Plastic, and Photoconductor radio buttons. On the right panel t he “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 0.5 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. Observe the movement of electrons in the circuit. It means current is flowing through the circuit. Observe the movement of electrons in the valence band.
Click on the Pause button.	Let us now pause the simulation.
Click the play button. Click the up arrow button of Battery Voltage to 0.5 V.	This simulation helps to understand the concept of conductivity. Observe that electrons are present in the circuit, but are not moving. Now click the Play button. 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. As voltage increases the potential difference between the terminals increases. The electrons now move faster and also move to higher energy levels.
Cursor on left panel.	The gap between the valence band and the conduction band is negligible in metals. So they overlap each other. This makes metals good conductors of electricity.
Click on the Plastic radio button. Point to band gap in the left panel. Point to Voltage box: 2 V. Click the Shine The Light checkbox.	Let us change the material to Plastic. Observe that the energy gap between the two bands has increased. We do not see the movement of electrons, even at high voltage. Now let us click the Shine The Light checkbox. Observe that even after shining light electrons are not moving.
Cursor on left panel.	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. Point to Voltage box: 2 V. Click the Shine The Light check box. Point to the movement of electrons. Point to the electrons in the higher energy level.	Let us change the material to Photoconductor. Even at high voltage no movement of electrons is seen. Let us shine the light now. We can now see the movement of electrons as light strikes the photoconductor. 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. 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 11 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.</div>
Slide Number 12 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: 13 About Spoken Tutorial Project	The video at the following link summarizes the Spoken Tutorial project. Please download and watch it.
Slide: 14 Spoken tutorial workshops	We conduct workshops using spoken tutorials and give certificates. For more details, please contact us.
Slide: 15 Answers for THIS Spoken Tutorial Do you have questions in THIS Spoken Tutorial? Please visit this site Choose the minute and second where you have the question. Explain your question briefly The spoken tutorial project will ensure an answer. You will have to register on this website to ask questions.	Please post your timed queries in this forum.
Slide: 16 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.