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

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|| '''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.

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|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'''.

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|02:23
| In the green panel we can also edit the values of '''Comparable resistor .''' It is the standard resistance of the circuit.

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|02:33
| '''Voltage of the power supply''' can take values from 1 to 10 '''Volts'''.

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|02:39
|We can also change the '''Resistance of the meter.'''

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|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'''

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|02:56
| Select both the check-boxes.

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|03:00
|Observe that the values of voltage and current are shown in the circuit.

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|03:06
| We can calculate the unknown resistance when the '''bridge''' is balanced.

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|03:12
| Let us now see how to balance the '''bridge'''.

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|03:16
| Press '''F5''' key on the keyboard to restart the '''App'''.

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|03:20
| Click on '''Indicate voltage '''and''' Indicate amperage''' check-boxes.

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|03:26
|To balance the '''bridge''', drag the sliding contact to get a zero '''amperage'''.

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|03:32
| We can also drag the slider in the green panel to change the '''amperage'''.

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|03:38
| Observe the value of voltage and current at each resistance.

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|03:44
|The values are balanced in series-parallel arrangement of resistances.

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|03:51
| At the point when '''amperage''' is zero, we can calculate the unknown resistance.

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|03:57
|At the bottom of the yellow panel, a message appears.
It reads “'''Now the resistance can be calculated”.'''

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|04:06
| '''Calculate resistance''' button is now active.

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|04:10
| Click on the '''Calculate resistance ''' button.

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|04:13
| In the white coloured box the value of unknown resistance is displayed.

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|04:19
| The measured value for '''Rx''' is 690 '''ohms'''. Here the value may change for you.

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|04:28
| Click on the '''New measurement '''button '''for measuring the next set of values'''.

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|04:34
| Again drag the sliding contact to zero.

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|04:38
| Click on '''Calculate resistance''' button.

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|04:41
| Observe the change in the value of unknown resistance. 

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|04:44
|This is because, '''galvanometer''' is a sensitive device.

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|04:50
|It will change the value every time when we click on the '''New measurement''' button.

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|04:56
| Press '''F5''' key on the keyboard to restart the '''App'''.

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|05:01
| Let us change the '''Comparable resistor''' to 1000 '''ohms'''.

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|05:06
| Observe that '''Resistance of the meter''' changes to 10 '''ohms'''.

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|05:11
| Now let us calculate the unknown resistance.

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|05:15
| The formula to calculate the unknown resistance is,

'''Rx ={R2/R1} x R3'''

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|05:25
| '''R1''' and '''R2''' are '''sliding resistance'''. '''R3''' is the '''comparable resistance'''.

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|05:33
| Change the '''Comparable resistance''' to 800 '''ohms ''' and press '''Enter'''.

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|05:39
| Again get the zero '''amperage''' by dragging the slider.

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|05:44
| Now in the formula substitute value of '''R1''' as 117.5 ohms, '''R2''' as 82.5 ohms and '''R3''' as 800 ohms.

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|05:57
| Here the calculated value of unknown resistance in 561.7 '''ohms'''.

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|06:05
| Here you can get a different value as the '''galvanometer''' is sensitive.

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|06:11
| Now let us compare with the value shown in the '''App'''.

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|06:15
| Click on the '''Calculate resistance '''button. Observe that the calculated value is comparable with the measured value.

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|06:24
| As an assignment solve this numerical.

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|06:29
| Let us explore the '''Potentiometer''' '''App'''.

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|06:33
| Follow the same steps to open the '''App'''.

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|06:37
| The interface opens with the '''potentiometer''' circuit.

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|06:42
| The '''potentiometer''' is a voltage divider used for measuring voltage. It is also used to control the flow of current.

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|06:53
| The circuit has three resistors.

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|06:56
| Here two resistors are connected in series and used as a '''sliding resistor'''.

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|07:03
| The third resistor is the '''Resistance of the '''appliance.'''

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|07:08
| The voltmeter is connected in parallel to the resistance.

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|07:13
| The voltmeter shows the output voltage of the circuit.

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|07:18
| A scale is provided to take the measurement of voltage at that particular point.

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|07:25
| The reading on scale is from 0.0 cm to 1.0 cm.

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|07:32
| Drag the '''Position of the sliding contact''' to 0.4 cm.

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|07:38
| The value of voltage at this point is 1.87 V(Volts).

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|07:44
| Now increase the '''Resistance of the appliance '''to 1000 '''ohms'''.

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|07:49
| Observe that the value of output voltage increased to 1.93 '''volts'''.

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|07:56
|If we increase the value of '''potentiometer''' resistance, output voltage increases.

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|08:03
| We can also calculate the voltage using the '''Ohm’s Law.'''

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|08:08
| Check the check-box '''Indicate amperage'''.

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|08:12
| Note that resistance till the point 0.4 cm is 39.5 '''ohms'''.

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|08:20
| So we can calculate voltage using formula 

'''V=IR'''

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|08:27
|I have already substituted the values of current and resistance from the '''App'''.

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|08:34
|The value for voltage is almost same as that for measured value.

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|08:40
| The graph is plotted for '''Voltage v/s length''' of the scale. 

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|08:45
| The blue point shows the value of voltage at point 0.4 '''cm'''.

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|08:52
| Change the value of '''Sliding resistor''' to 1000 '''ohms''' and press '''Enter'''.

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|08:59
| Observe that the value of current has decreased to 0.004 A.

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|09:07
| So here we can say that '''potentiometer''' controls the flow of current.

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|09:13
| Let us make a tabular column to study a graph of '''voltage v/s length'''.

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|09:19
| Press '''F5''' key on the keyboard to restart '''App'''.

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|09:24
| Change the value of '''Voltage of the power supply''' to 10 '''V''' and press '''Enter'''.

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|09:31
| Drag the '''sliding contact''' to 0.0 cm. The resistance and voltage at this point are zero.

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|09:41
| Drag the '''sliding contact''' to 0.1 '''cm'''. Click on the '''Indicate amperage''' check box.

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|09:50
| Tabulate the values of '''length''', '''current''' and '''voltage''' in the tabular column. 

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|09:56
| Drag sliding contact to 0.2 cm and tabulate the values in the table.

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|10:04
|Similarly take four more values and enter these values in the table.

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|10:10
| Here is the completed table.

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|10:13
|Observe that if length increases the output voltage also increases.

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|10:19
|Hence the graph is linear.

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|10:23
| As an assignment 

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|10:25
|Change the values of resistance of the appliance to 500 '''ohms''', 700 '''ohms''' and 800 '''ohms'''.

Find the output voltage.

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| 10:38
|Let us summarise

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|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.
|-
|}