A meter bridge is observed to be a simple form of potentiometer that is used in science laboratories in schools and colleges. This device is very useful in the determination of the principle of measurement of resistance by potentiometric means.
We use a resistance box as R and an unidentified resistance as “S” to connect across the 2 gaps of metallic copper strips. Now connect one of the ends of the galvanometer device to the mid lead of a metallic strip.
To perform a meter bridge experiment, the wire is made up of manganin or constantan because of its high resistivity or specific resistance. The material constantan was started to be used in performing experiments by Edward Weston in the year 1892. Foil made up of Manganin is mostly used in the formation of resistors, especially ammeter shunts. This is because of the virtually 0 temperature co-efficient of the value of the resistance and its longer-term stability.
Thick strips of copper are used in this bridge as copper is considered to be a favourable conductor of electricity. The reason for using broad metal strips in the Meter Bridge is to lessen the amount error measured in the unknown resistance’s value.
The reason why this bridge is called as Meter Bridge is because of the fact that it works on the Wheatstone bridge’s principle. So, people also popularly call it as Wheatstone's meter bridge. Another thing is that the wire length used in this circuit is of 1 meter, so it has got its name as a meter bridge.
One of the commonest forms of errors that are reported in the meter bridge experiment is the shifting of 0 on the galvanometer scale at varying points and the stray resistance that results into the formation of end error in the wire of the meter bridge wire.
There is a null point observed in case of a meter bridge experiment. This “null point” is located at a distance of forty centimeters from the point A. On application of a resistance of magnitude 12 ohm to the circuit in parallel to the variable resistance, a null point is formed and measured at 50.0 cm from A.
Balancing length is an important concept in a meter bridge experiment. The value of balancing length “l” is seen to remain constant when the radius of the meter bridge wire gets doubled and keeping the cross-section area of the wire uniform. This happens due to the relation R/X = l/(100−l), being independent of the cross-section area of the wire. Here, X is an unknown resistance.
Wheatstone bridge is one of the most popular bridges in the history of science. There are several different applications of this bridge in invention of various new scientific principles. The use of this bridge includes thermistor, strain gauge, light detector, potentiometer, etc. Wheatstone bridge also has its significance in an operational amplifier due to its ability to measure and magnify the tiny changes that occurs in resistors.
Both potentiometer and a meter bridge are widely used devices in the calculation of several scientific theories and inventions. They have a huge significance in science. A Meter Bridge is a kind of an electric device that assists in the measurement of an unidentified resistance.