Apps-On-Physics/C3/Wheatstone's-Bridge-and-Potentiometer/English-timed

Time	Narration
00:01	Welcome to the spoken tutorial on Wheatstone Bridge and Potentiometer.
00:07	At the end of this tutorial you will be able to, Simulate the working of wheatstone bridge. Solve a numerical based on wheatstone bridge.
00:18	Simulate the working of potentiometer. Solve a numerical based on potentiometer.
00:27	Here I am using, Ubuntu Linux OS version 16.04 Firefox Web Browser version 62.0.3
00:40	To follow this tutorial, learner should be familiar with Apps on Physics. For the Pre-requisites tutorials please visit this site.
00:51	In this tutorial we will use, Wheatstone's Bridge and Potentiometer Apps.
00:59	To open the App, right-click on wheatstonebridge_en.htm file. Select Open with Firefox Web Browser option.
01:12	The App opens in the browser.
01:15	Wheatstone’s bridge is a simple circuit for measuring the unknown resistance.
01:21	Meter bridge uses the same principle for practical purpose. First we will learn about the circuit connections.
01:31	The circuit shows a simple series-parallel arrangement of resistances.
01:37	The resistances are connected between the voltage supply and ground.
01:43	A galvanometer is connected between the two parallel branches of resistances.
01:49	Galvanometer is a device to detect small changes in current in the circuit.
01:56	The negative terminal of the galvanometer is connected to the wire of 1 cm.
02:03	The measurement of the wire is shown by the scale. We can drag the sliding contact along the wire.
02:11	In the green panel the Sliding resistor is that of the wire.
02:17	We can vary the Sliding resistor from 1 ohm to 1000 ohms.
02:23	In the green panel we can also edit the values of Comparable resistor . It is the standard resistance of the circuit.
02:33	Voltage of the power supply can take values from 1 to 10 Volts.
02:39	We can also change the Resistance of the meter.
02:43	Resistance of the meter depends on the comparable resistor.
02:48	At the bottom of control panel there are two check boxes. Indicate voltage and Indicate amperage
02:56	Select both the check-boxes.
03:00	Observe that the values of voltage and current are shown in the circuit.
03:06	We can calculate the unknown resistance when the bridge is balanced.
03:12	Let us now see how to balance the bridge.
03:16	Press F5 key on the keyboard to restart the App.
03:20	Click on Indicate voltage and Indicate amperage check-boxes.
03:26	To balance the bridge, drag the sliding contact to get a zero amperage.
03:32	We can also drag the slider in the green panel to change the amperage.
03:38	Observe the value of voltage and current at each resistance.
03:44	The values are balanced in series-parallel arrangement of resistances.
03:51	At the point when amperage is zero, we can calculate the unknown resistance.
03:57	At the bottom of the yellow panel, a message appears. It reads “Now the resistance can be calculated”.
04:06	Calculate resistance button is now active.
04:10	Click on the Calculate resistance button.
04:13	In the white coloured box the value of unknown resistance is displayed.
04:19	The measured value for Rx is 690 ohms. Here the value may change for you.
04:28	Click on the New measurement button for measuring the next set of values.
04:34	Again drag the sliding contact to zero.
04:38	Click on Calculate resistance button.
04:41	Observe the change in the value of unknown resistance.
04:44	This is because, galvanometer is a sensitive device.
04:50	It will change the value every time when we click on the New measurement button.
04:56	Press F5 key on the keyboard to restart the App.
05:01	Let us change the Comparable resistor to 1000 ohms.
05:06	Observe that Resistance of the meter changes to 10 ohms.
05:11	Now let us calculate the unknown resistance.
05:15	The formula to calculate the unknown resistance is, Rx ={R2/R1} x R3
05:25	R1 and R2 are sliding resistance. R3 is the comparable resistance.
05:33	Change the Comparable resistance to 800 ohms and press Enter.
05:39	Again get the zero amperage by dragging the slider.
05:44	Now in the formula substitute value of R1 as 117.5 ohms, R2 as 82.5 ohms and R3 as 800 ohms.
05:57	Here the calculated value of unknown resistance in 561.7 ohms.
06:05	Here you can get a different value as the galvanometer is sensitive.
06:11	Now let us compare with the value shown in the App.
06:15	Click on the Calculate resistance button. Observe that the calculated value is comparable with the measured value.
06:24	As an assignment solve this numerical.
06:29	Let us explore the Potentiometer App.
06:33	Follow the same steps to open the App.
06:37	The interface opens with the potentiometer circuit.
06:42	The potentiometer is a voltage divider used for measuring voltage. It is also used to control the flow of current.
06:53	The circuit has three resistors.
06:56	Here two resistors are connected in series and used as a sliding resistor.
07:03	The third resistor is the Resistance of the appliance.
07:08	The voltmeter is connected in parallel to the resistance.
07:13	The voltmeter shows the output voltage of the circuit.
07:18	A scale is provided to take the measurement of voltage at that particular point.
07:25	The reading on scale is from 0.0 cm to 1.0 cm.
07:32	Drag the Position of the sliding contact to 0.4 cm.
07:38	The value of voltage at this point is 1.87 V(Volts).
07:44	Now increase the Resistance of the appliance to 1000 ohms.
07:49	Observe that the value of output voltage increased to 1.93 volts.
07:56	If we increase the value of potentiometer resistance, output voltage increases.
08:03	We can also calculate the voltage using the Ohm’s Law.
08:08	Check the check-box Indicate amperage.
08:12	Note that resistance till the point 0.4 cm is 39.5 ohms.
08:20	So we can calculate voltage using formula V=IR
08:27	I have already substituted the values of current and resistance from the App.
08:34	The value for voltage is almost same as that for measured value.
08:40	The graph is plotted for Voltage v/s length of the scale.
08:45	The blue point shows the value of voltage at point 0.4 cm.
08:52	Change the value of Sliding resistor to 1000 ohms and press Enter.
08:59	Observe that the value of current has decreased to 0.004 A.
09:07	So here we can say that potentiometer controls the flow of current.
09:13	Let us make a tabular column to study a graph of voltage v/s length.
09:19	Press F5 key on the keyboard to restart App.
09:24	Change the value of Voltage of the power supply to 10 V and press Enter.
09:31	Drag the sliding contact to 0.0 cm. The resistance and voltage at this point are zero.
09:41	Drag the sliding contact to 0.1 cm. Click on the Indicate amperage check box.
09:50	Tabulate the values of length, current and voltage in the tabular column.
09:56	Drag sliding contact to 0.2 cm and tabulate the values in the table.
10:04	Similarly take four more values and enter these values in the table.
10:10	Here is the completed table.
10:13	Observe that if length increases the output voltage also increases.
10:19	Hence the graph is linear.
10:23	As an assignment
10:25	Change the values of resistance of the appliance to 500 ohms, 700 ohms and 800 ohms. Find the output voltage.
10:38	Let us summarise
10:40	In this tutorial we have, Simulated the working of wheatstone bridge. Solved a numerical based on wheatstone bridge. Simulated the working of potentiometer Solved numerical based on potentiometer
10:59	These Apps were created by Walter-fendt and his team.
11:04	The video at the following link summarizes the Spoken Tutorial project. Please download and watch it.
11:12	The Spoken Tutorial Project team,conducts workshops gives certificates. For more details, please write to us.
11:22	Please post your timed queries in this forum.
11:26	Spoken Tutorial Project is funded by MHRD, Government of India.
11:32	This is Himanshi Karwanje from IIT-Bombay. Thank you for joining.

Contributors and Content Editors

Pratik kamble