May 5, 2012

How to find the resistance of Galvanometer: Half Deflection method

Using Half Deflection method to find the resistance of Galvanometer, This experiment is performed by the 1st semester University students of COMSATS.

The purpose of sharing this experiment process is to help fellow students for preparation of their Physics lab manuals.

This experiment is performed in the Campus Phusics lab.

Experiment # 1

Finding the resistance Of Galvanometer by Half Deflection method

Apparatus: Galvanometer, High Resistance Box (HRB), Low Resistance Box (LRB), Battery, one way keys, connecting wires and sand paper.

Circuit Diagram

Galvanometer: Galvanometer is a type of measuring device that can be used to detect current in the circuit.

  1. First of all I make the complete circuit, as shown in the diagram, by connecting Galvanometer, HRB, LRB and Keys with the help of connecting wires.
  2. HRB is in series and LRB is parallel to Galvanometer.
  3. I connected the circuit to the DC power supply through key K1.
  4. 1st I took some resistance from HRB and close the key K1, I noted the some deflection in galvanometer. I adjusted the resistance RH of HRB in such a way that galvanometer showed full deflection i.e. 30 divisions.
  5. Then I closed the second key K2, deflection on scale becomes Zero. I adjusted RL resistance of LRB in such a way that galvanometer shows half deflection i.e. 15 divisions. I noted RL.
  6. Now I repeated the whole procedure and adjusted the resistance of HRB and LRB is such a way that deflection in galvanometer becomes 28 divisions and 14 divisions respectfully.
  7. I repeated this procedure several times for full deflections of 26,24 and 22 divisions in galvanometer and for half deflections of 13, 12 and 11 divisions.
I calculated resistance of RG of galvanometer by using formula.

I also used kirchoff's voltage law and Ohm,s Law.

I noted all the values in the above table.

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