Apps-On-Physics/C3/Magnetism-and-Electromagnetism/English-timed

Time	Narration
00:01	Welcome to the Spoken Tutorial on Magnetism and Electromagnetism.
00;07	At the end of this tutorial you will be able to,
00:11	Draw magnetic field lines for a bar magnet.
00:15	Verify right hand thumb rule.
00:18	Verify Fleming's left hand and right hand rules.
00:23	Simulate the working of a generator.
00:26	Here I am using, Ubuntu Linux OS version 16.04
00:32	Firefox web browser version 62.0.3
00:38	To follow this tutorial, learner should be familiar with Apps on Physics.
00:43	For the pre-requisites tutorials please visit this site. https://spoken-tutorial.org/
00:49	In this tutorial we will use, Magnetic Field of a Bar Magnet
00:56	Magnetic Field of a Straight Current-Carrying Wire
01:00	Lorentz Force and Generator Apps.
01:04	I have already downloaded Apps on Physics to my Downloads folder.
01:09	Right click on magneticfieldbar_en.htm file.
01:15	Select Open With Firefox web Browser option.
01:19	Magnetic field bar App opens.
01:22	The App opens showing a magnet and a magnetic needle.
01:28	On the green panel there are two buttons. Clear field lines and Turn magnet.
01:35	Poles of a bar magnet and compass needle are represented by the following colors.
01:41	Red for north pole and green for south pole.
01:46	Click on Turn magnet button.
01:49	Observe that both bar magnet and magnetic needle change their direction.
01:55	Let us draw the magnetic field lines. Place the cursor on the magnetic needle.
02:02	Click on the magnetic needle and move the needle up and down to draw the magnetic lines.
02:09	Continue to draw the lines as shown here.
02:13	Click on the Clear field lines button.
02:17	Click on Turn magnet button.
02:20	Again draw the magnetic lines around the magnet.
02:25	When we turn the magnet, the lines of force change the direction.
02:30	The direction of magnetic field outside the bar magnet is from north to south. It is shown by the arrows.
02:39	Magnetic field is strongest inside the bar magnet.
02:44	Outside the bar magnet it is strongest near the poles.
02:49	What is the direction of magnetic field inside the bar magnet?
02:55	Next we will move on to Magnetic Field Line in a Current Carrying Wire App.
03:00	Right click on magneticfieldwire_en.htm file.
03:06	Select Open with Firefox Web browser option.
03:10	The App opens showing magnetic field lines around a current carrying wire.
03:16	On the right side of the screen we have a Reverse current button.
03:22	The red arrow indicates the direction of the current. Note that the direction of current is opposite to that of electrons.
03:33	The signs at the end of the wire symbolizes the terminals of the connected battery.
03:40	The concentric circles are the magnetic field around the current carrying wire.
03:46	Let us find the direction of magnetic field using right hand thumb rule.
03:53	Observe the picture and put your right hand as follows.
03:58	Put your right hand thumb in the direction of the current.
04:03	Now curl your fingers inside.
04:07	Fingers gives you the direction of magnetic field.
04:12	As an assignment, Reverse the current flow and determine the magnetic field.
04:19	Let us move on to the next App, Lorentz Force.
04:24	Follow the same steps as we used for previous App to open htm file.
04:31	Interface shows a horseshoe magnet through which a conducting wire is passed.
04:37	The blue arrows shows the direction of the magnetic field.
04:42	On the green panel we have the following buttons. On/Off , Reverse current and Turn magnet.
04:51	When the circuit is open, the wire is shown in black colour.
04:56	Click on the On/Off button to complete the circuit.
05:01	Notice that the wire is in conduction mode.
05:06	This is indicated by the red coloured wire.
05:10	At the bottom, there are three check-boxes. These are Current direction, Magnetic field and Lorentz force.
05:20	The black arrow pointing towards right is the Lorentz force.
05:26	Lorentz force is always perpendicular to the magnetic field.
05:31	To change the direction of magnetic field, click on the Turn magnet button.
05:38	Let us verify the direction of Lorentz force using Fleming’s left-hand rule.
05:45	Press F5 key on the keyboard to restart the App.
05:50	First uncheck the Lorentz force check-box.
05:54	Click on On/Off button.
05:57	Now keep your fingers of the left hand as suggested here.
06:03	Index finger pointing in the direction of magnetic field. Middle finger pointing in the direction of current.
06:13	Thumb shows the direction of Lorentz force.
06:17	Here the direction of Force is towards the right-side. This is Fleming’s left-hand rule.
06:25	Let us verify our answer by checking the Lorentz force check-box.
06:31	Observe that the direction is same as shown in the App.
06:36	As an assignment Reverse the current flow.
06:40	Determine the direction of lorentz force using Fleming’s left hand rule.
06:47	Now let us open the Generator App.
06:51	I will open the App as before.
06:55	The App shows a generator.
06:58	An electrical generator converts mechanical energy into electrical energy.
07:05	The App opens showing a horseshoe magnet.
07:09	A rectangular current carrying coil is inserted between the poles of the magnet.
07:15	On the green panel, we can change the rotations per minute using the slider.
07:22	By default the rectangular coil rotates 6 rotations per minute.
07:28	We can change the rotation of the coil to a maximum of 12 rotations per minute.
07:35	Increase the rotation to 12 rotations per minute.
07:40	In the graph we can see two complete cycles in one minute.
07:46	Here the frequency of the maximum output voltage is doubled.
07:52	The rectangular coil is connected to the voltage source through the slip rings.
07:58	Observe that the rectangular coil is rotating about an axis. This coil is perpendicular to the magnetic field.
08:09	Here rotation of the rectangular coil is a source of mechanical energy.
08:16	Due to the rotation of the coil, current is induced into the wire.
08:22	The red arrow represents the direction of the induced current.
08:27	In the green panel we can choose an AC generator or DC generator.
08:34	By default Without commutator an AC generator is selected.
08:40	Select With commutator radio button.
08:44	Commutator is a device for reversing the direction of flow of current.
08:50	This device ensures that the current flows only in direct current mode.
08:57	Hence With Commutator means, the generator is a DC generator.
09:03	On the top of the circuit, voltage v/s time graph is plotted.
09:09	This is the graph of a DC generator.
09:13	In the graph, moving blue point indicates the change in voltage.
09:19	Change direction button changes the direction of the rectangular coil.
09:25	Click on the Change direction button.
09:28	Observe the change in the direction of rectangular coil. Also notice the change in the graph.
09:37	Press F5 key on the keyboard to restart the App.
09:42	We can find the direction of induced current using Fleming’s right-hand rule.
09:49	This rule is same as Fleming’s left-hand rule.
09:53	Click on the Pause button.
09:56	Now arrange fingers of your right hand as shown in the figure.
10:01	We can determine the direction of magnetic field using Fleming's right hand rule.
10:07	There are three check-boxes at the bottom of the green panel.
10:12	Direction of movement, Magnetic field and Induced current.
10:18	Uncheck the Magnetic field check-box. Notice that the magnetic field lines disappear.
10:27	In the similar way we can uncheck the remaining check-boxes if not required.
10:33	Press F5 key on the keyboard to restart the App.
10:38	AC generator is an alternating current generator.
10:43	So, here the graph shows positive as well as negative voltages.
10:49	As an assignment, Change the rotations per minute to 0, 3.0, 6.0 and 9.0
10:57	Note the changes in the movement of the coil and graph. Explain the reason for the changes.
11:06	Let us summarise
11:08	Using these Apps we have, Drawn magnetic field lines of a bar magnet.
11:15	Verified right hand thumb rule.
11:18	Verified Fleming's left hand and right hand rules.
11:23	Simulated the working of a generator.
11:28	These Apps were created by Walter Fendt and his team.
11:33	The video at the following link summarises the Spoken Tutorial project. Please download and watch it.
11:41	The Spoken Tutorial Projectteam, conducts workshops and gives certificates. For more details, please write to us.
11:51	Please post your timed queries in this forum.
11:55	The Spoken Tutorial Project is funded by MHRD, Government of India.
12:01	This is Himanshi Karwanje from IIT-Bombay. Thank you for joining.

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