An electromechanical instrument that is used for noticing & signifying an electric current is known as a galvanometer. Simply put, we can say that it is used to detect small electric currents or measure their magnitude. The current and its intensity are usually indicated by a magnetic needle’s movement or that of a coil in a magnetic field which is an important part of a galvanometer.

The main function of the galvanometer is to decide the current’s existence, direction, and strength in an element/circuit. This works on the rule of converting electrical energy into mechanical energy.

Some of the different types of galvanometer include Tangent galvanometer, Astatic galvanometer, Mirror galvanometer and Ballistic galvanometer. However, today, the main galvanometer type used widely is the D’Arsonval/Weston type or the moving coil type. 

What is Voltmeter? 

The instrument which measures the voltage or potential difference in volts is known as the voltmeter.

A galvanometer is converted into a Voltmeter by connecting a large resistance in series with the galvanometer. It works on the principle that the torque is generated by the current which induces because of measured voltage and this torque deflects the pointer of the instrument. The deflection of the pointer is directly proportional to the potential difference between the points. The voltmeter is always connected in parallel with the circuit/element across which the potential difference has to be measured.

Relation between Galvanometer & Voltmeter

 A galvanometer is a type of sensitive ammeter or digital multimeter for detecting electric current. Galvanometers were the first instruments used to detect and measure electric currents. A galvanometer can be converted into a voltmeter by connecting a high-resistance in-series connection. The scale is calibrated in volt. The value of the resistance connected in series decides the range of the voltmeter.

How can you transform Galvanometer to Voltmeter?

A galvanometer can be converted into a voltmeter by connecting a high-resistance in-series connection. The scale is calibrated in volt. The value of the resistance connected in series decides the range of the voltmeter.

Galvanometer resistance =G

The current required to produce full-scale Deflection in the galvanometer =Ig

Range of voltmeters =V

Resistance of voltmeter =R

Since R is connected in series with the galvanometer, the current through the galvanometer,

Ig=R+GV

∴ R=V/Ig −G

The resistance is calculated by this equation which is connected in series. The effective resistance of the voltmeter is Rv=G+R. Rv is very large, and hence a voltmeter is connected in parallel in a circuit as it draws the least current from the circuit.

Applications of Galvanometer Vs Voltmeter

Galvanometer	Voltmeter
It is used to detect the flow of the current’s direction within the circuit & also determines the null point.	Using this, we can determine the voltage between two points in the circuit.
They are used in control systems, laser engraving, TVs, laser sintering, and displays.	It can be used just to tell whether there is power in a circuit or not, such as a mains outlet.
They are used in the CD/DVD players & hard drives for controlling the position of head servos.	We can calculate the current by measuring the voltage across a known resistance. This is useful when you don’t have an ammeter.
They are used in a film camera to get the readings of the photoresistor in the metering mechanisms	They are used to build a continuity checker with a series battery.
They are used to build ammeters and voltmeters.	They are used to build an ohm meter by using a voltage divider with an unknown resistor.

Transforming Galvanometer to Voltmeter Experiment

Experiment Title – Convert a Given Galvanometer Into a Voltmeter

Experiment Description – What do we do when our voltmeter suddenly breaks down? In this experiment, we will convert a given galvanometer of known resistance and figure of merit into a voltmeter.

Aim of Experiment – To convert a given galvanometer of known resistance and figure of merit into a voltmeter of desired range and to verify the same.

Material Required – 

1. A galvanometer of known resistance and figure of merit
2. A battery or a battery eliminator.
3. One-way key.
4. A rheostat of range of 200 ohms.
5. Resistance box.
6. A voltmeter of 3 V range.
7. Connecting wires and sandpaper.

Procedure – 

1. Using the given values of V_o, I_g, and G, find the series resistance R

2. Connect a cell, the converted galvanometer and a voltmeter of nearly the same range in parallel with a high resistance rheostat Rh to make the connections.

3. Close the key K and adjust the rheostat until the voltage shown in the voltmeter equals the desired range of 3 V. In Addition, adjust the position of the slider of the rheostat and the resistance from the resistance box so that the voltmeter shows 3 V when the galvanometer shows a full-scale deflection. Observe the resistance box and record the total resistance.

Precautions – 

1. Make sure that the resistance box used is of high resistance.
2. Use the rheostat as a potential divider.
3. Make sure to use a high resistance of 10 kΩ from the resistance box before closing the battery key to avoid damage to the galvanometer.
   
   

FAQs on Transforming Galvanometer to Voltmeter