Moving Coil Galvanometer-
Before you go through this article, make sure that you have gone through the previous article on Moving Coil Galvanometer.
We have learnt-
- A galvanometer is an instrument that is used to detect small currents in an electric circuit.
- An ordinary galvanometer gives a full scale deflection with a small current of few μA.
In this article, we will learn the conversion of a galvanometer into a voltmeter.
Voltmeter-
- A voltmeter is a device used to measure potential difference across any two points in an electric circuit.
- It is always connected in parallel with the circuit element across which the potential difference is to be measured.
- A voltmeter is designed to have very high effective resistance.
- An ideal voltmeter has infinite resistance.
Conversion of Galvanometer Into Voltmeter-
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To convert a galvanometer into a voltmeter, A high resistance of suitable value is connected in series with the galvanometer. |
The value of high resistance depends on the desired range of the voltmeter.
Diagram-
The following diagram shows the conversion of a galvanometer into a voltmeter-
Calculating Value of High Resistance-
Let-
- Rg = Resistance of the galvanometer
- R = High resistance to be connected in series
- Ig = Full scale deflection current i.e. current required to produce full scale deflection in the galvanometer
- 0-V = Desired range of the voltmeter
Using Ohm’s law, we must have-
V = Ig x (Rg + R)
From here, the value of high resistance is given by-
Important NoteBefore converting a galvanometer into a voltmeter of desired range, we must know-
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Effective Resistance-
The effective resistance of the converted voltmeter is given by-
MCQs Quiz-
MCQs Quiz on Conversion of Galvanometer into Voltmeter
Worksheet-
Worksheet on Conversion of Galvanometer into Voltmeter
Get more notes & other study material of the Chapter Moving Charges & Magnetism.
