Expert please explain the concept of Ammeter, Voltmeter & Galvanometer
A galvanometer is a device that is used to detect the presence of small electric current and it's direction. The current and its intensity is usually indicated by a magnetic needle’s movement or that of a coil in a magnetic field that is an important part of a galvanometer.
The moving coil galvanometer is the most common type.It works on the principle that when a current carrying coil is placed in a magnetic field,it experiences a net torque.Figure below shows the diagram of a moving coil galvanometer.
Voltmeter is a device that is used to measure the of potential difference between two points in a circuit.It is always connected in parallel to a circuit.A voltmeter is of very high resistance.A galvanometer can be converted into a voltmeter by connecting a high resistance in series with it.
Ammeter is a device used to measure the current flowing through a circuit.It is always connected in series to a circuit.An ammeter is of low resistance.So a galvanometer can be converted into an ammeter by connecting a low resistance in parallel to it.
A galvanometer is an electrical device which can detect the presence of current in a circuit. A galvanometer can also be modified to use it as a voltmeter (voltage measuring device) or an ammeter (current measuring device).An ammeter is an instrument that is used to measure the currents in a circuit. A voltmeter is an instrument that is used to measure the voltage between two points in a circuit.
The galvanometer coil has a moderate resistance (about 100 ohms) and the galvanometer itself has a small current carrying capacity (1 mA).
An ammeter is a device (instrument) used for measuring large electric currents in ‘ circuits. For this purpose, it is put in series with the circuit in which the current is to be measured.
For accurate measurement, an ammeter must have following two properties:
- A very small resistance (zero in ideal case).
- A very large current carrying capacity.
It is done by connecting low resistance in parallel with the coil of the galvanometer. This parallel low resistance is called shunt. The shunt reduces the overall resistance of the ammeter and increases its current carrying capacity.
A voltmeter is a device (instrument) used for measuring electric potential difference between two points in a circuit. For this purpose, it is put in parallel with that branch of circuit, at the ends of which the potential difference is to be measured.
For accurate measurements a voltmeter must have following two properties:
- A very large resistance (infinite in ideal case).
- A very small current carrying capacity.
It is done by connecting a high resistance in series with the coil of the galvanometer. The series high resistance increases the overall resistance of the voltmeter and reduces its current carrying capacity.