What is Wheatstone bridge Chemistry class 12th

 

In Class 12 Chemistry, the Wheatstone Bridge is not a core chemistry concept—it is actually a concept from Physics (Class 12 Physics, Chapter: Current Electricity). However, it can be related to electrochemical measurements, such as in the determination of resistance in electrolytic conductance experiments.

🔌 Wheatstone Bridge – Definition (Physics Concept)

The Wheatstone Bridge is an arrangement of four resistors in a diamond shape that is used to measure an unknown electrical resistance accurately by balancing two legs of a bridge circuit.

🧪 Relation to Chemistry (Electrochemistry)

In Electrochemistry, the Wheatstone Bridge is used in conductivity cells to measure the resistance of an electrolyte solution, which is further used to calculate:

  • Specific Conductance (κ)
  • Molar Conductance (Λm)
  • Equivalent Conductance (Λeq)

⚙️ How it works in Chemistry (Conductivity Cell)

  1. The solution is placed between two electrodes.
  2. An AC (alternating current) source is connected through a Wheatstone Bridge setup.
  3. The bridge is balanced using a variable resistance.
  4. When the bridge is balanced (no current through the galvanometer), the resistance of the electrolyte solution can be calculated.
  5. Using the cell constant, we find conductivity.

📝 Formula Used

In balanced condition:


\frac{R_1}{R_2} = \frac{R_3}{R_x}

Where:

  • = Unknown resistance (like electrolyte resistance)
  • The other are known resistors

📚 In NCERT Chemistry Class 12

The Wheatstone Bridge is indirectly mentioned in the context of:

  • Measurement of conductance of ionic solutions
  • Determination of conductivity using a conductivity cell

Look in Chapter 3: Electrochemistry, under:

"Measurement of the Conductivity of Ionic Solutions"

📌 Summary

Topic Details
Subject Physics (but used in Chemistry)
Use in Chemistry To measure resistance of electrolyte solution
Concept Used Balancing resistances in a bridge circuit
Related NCERT Topic Chapter 3: Electrochemistry


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