Apps-On-Physics/C3/Wheatstone's-Bridge-and-Potentiometer/English-timed
From Script | Spoken-Tutorial
| 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. |
