CircuitJS/C2/Wheatstone-Bridge/English

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Visual Cue Narration
Slide:1 Welcome to the spoken tutorial on Wheatstone Bridge usingCircuitjs simulator.
Slide 2:

Learning Objective

In this tutorial, we will learn how,
  • Wheatstone Bridge is used to measure the unknown resistance in the circuit
  • To check the balance condition of Wheatstone Bridge
Slide 3:

System Requirement

To record this tutorial, I am using:
  • Ubuntu Linux 20.04 OS
  • CircuitJS Application
Slide 4:

Prerequisite

To follow this tutorial, you should have a basic knowledge of,
  • Electrical circuits
Wheatstone.png We will make this circuit for the Wheatstone Bridge demonstration.
For a Wheatstone Bridge circuit, we require,
  • 4 Resistors
  • 1 DC Power supply of 12 Volts
  • 1 Switch and
  • 1 Ammeter
Click on File and select New Blank Circuit. Let us open the Circuitjs interface.

In the menu bar, click on File and select New Blank Circuit.

Click on the Draw option >> select Add resistor.

Click and drag to draw a resistor.

Right-click on the resistor >> select the Duplicate option.

Click on the Draw option and select Add resistor.

Click and drag to draw a resistor as shown.

By default, the value of this resistor is 1 Kilo Ohm.

We need 4 resistors for this circuit.

Right-click on the resistor, and select the Duplicate option.

This will generate a resistor of the same value.

Repeat this process till you have 4 resistors in the work area.

Align all these resistors in the same manner as shown.

Make sure they all are connected.

Select Add text option. Use the Add Text option to give labels to these multiple resistors.

Give the labels as P, Q, R, and S respectively as shown.

Point to junction After this connection, we can see that multiple junctions are formed.

To denote these junctions use the Add Text option to label them.

Give labels as A,B, C, and D to these junctions as shown.

Show the path to find the DC power supply and draw it

Click on Draw, >> Inputs and Sources >>select Add Voltage Source (2-terminal). Change the DC power supply value

Next, we have to include the DC power supply.

Click on Draw, go to Inputs and Sources.

Select Add Voltage Source (2-terminal).

Drag and draw the DC power supply in the working area.

Change the voltage value of theDC power supply to12V.

Click onDraw >> go to thePassive Component.

Select the Switch component.

Drag and draw the Switch in the work area.

We also need a Switch to turn ON and OFF the circuit.

Click onDraw and go to thePassive Components.

Then select Add Switch to select the switch component.

Drag and draw the Switch in the work area.

Connect the switch in series with the DC power supply.

Point the Wheatstone bridge circuit. In an ideal Wheatstone Bridge circuit, a galvanometer is used to calculate the current.

As Circuitjs platform does not have a galvanometer component, we will use an Ammeter.

Click on Draw, go to Outputs and Labels

Select the Add Ammeter.

Point to the circuit.

Click on Draw, go to Outputs and Labels.

Select the Add Ammeter.

Draw it by dragging the cursor in the working area.

Connect the Ammeter between junctions B and D as shown in the circuit.

Cursor in the work area. We have all the required components in the work area.

Now let's connect the components using wires.

From the Draw menu, select Add wire.

Drag and draw a wire

From the Draw menu, select Add wire.

Drag and draw a wire by selecting the end points of the components as shown in the video.

Connect the junction A to the DC power supply.

Connect the junction C to the switch.

Observe the yellow dots in the circuit. Observe the yellow dots indicating the current flow direction in the circuit.

If you cannot see the yellow dots moving consistently, increase the current speed bar.

The current speed bar is available at the right-top corner of your screen.

Change the P,Q,R,S resistor values to 200, 400 and 400 ohms respectively Let us now change the value of these resistors.

Change the values of resistor P to 200 ohms.

Change the value of resistor Q and R to 400 ohms.

Let S be the unknown resistor.

Ignore the value of resistor S shown in the circuit.

Notice that the current value shown by the ammeter is 1.36 milli amperes.

Slide:

Wheatstone Bridge - Balanced condition

The Wheatstone Bridge is in a balanced condition, when the below conditions are fullfilled.
  • Ratio of resistance is P/Q = R/S, and
  • The current flowing through the ammeter is Zero.
Slide: Find unknown resistance

Wheatstone-balance.png

P = 200 Ohms Q = 400 Ohms R = 400 Ohms S = ?

Let us find the value of resistor S using the Wheatstone Bridge balanced condition formula.

The values of resistors are, P = 200 Ohms

Q = 400 Ohms

R = 400 Ohms

S = is unknown

The balanced condition formula P/Q = R/S becomes,

S = R x Q / P

Put the values of these resistors in the formula.

After calculation, the value of resistor S is 800 Ohms.

CircuitJS simulation window

Point to ammeter value

Now, let us go back to the Circuitjs simulation.

Let us change the value of resistor S to 800 ohms using the edit option.

Now the ammeter shows zero value.

This shows the Wheatstone Bridge is in balanced condition.

This brings us to the end of the tutorial.

Let us summarize.

Slide Summary In this tutorial, we learnt how
  • The Wheatstone Bridge is used to measure unknown resistance in the circuit
  • To check the balance condition in Wheatstone Bridge.
Slide:

Assignment

As an assignment,

Change the values of resistor P to 60 ohms, resistor Q to 150 ohms, resistor R to 300 ohms.

Use the Wheatstone Bridge balance condition formula to find the value of resistor S.

Slide :

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Acknowledgement Spoken Tutorial project was established by the Ministry of Education(MoE), Govt of India
Thank you This tutorial has been contributed by FOSSEE and Spoken Tutorial Project, IIT Bombay.

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Contributors and Content Editors

Madhurig, Nirmala Venkat