What is the principle of meter bridge?
Answers
Answer:
A Meter Bridge is also called as slide wire bridge and is an instrument that works on the principle of a Wheatstone bridge. A meter bridge is used to find the unknown resistance of a conductor as that of in a Wheatstone bridge.
In the above figure, R is called as the Resistance, P is the Resistance coming across AB, S is the Unknown Resistance, Q is the Resistance between the joints BD.
AC is long wire of length a 1m made of constantan or manganin having a uniform area of the cross-section Such that L1 + L2 = 100
Assuming that L1 = L => L2 = 100 – L
Relation obtains the unknown resistance ‘X’ of the given wire: X = RL2/L1 = R(100 – L)/L
And the specific resistance of material for a given wire is obtained by the relation = (3.14) r2X/l
where, r = the radius of the cable and also l = length of the wire.
Samuel Hunter Christie created this instrument in the year 1833 and was improved and also simplified by Sir Charles Wheatstone in the year 1843. The digital multimeters in today’s world provide the simplest forms in measuring the resistance. The Wheatstone Bridge can be still used in measuring light values of resistances around the range of milli-Ohms.
Explanation:
The meter bridge principle is based on the
Wheatstone Bridge circuit which says that if
at any point or length (of a wire), the ratio of two resistances (say R1 and R2) is equal to the ratio of another two resistances (say R3 and R4 where R4 is the unknown resistance), then there shall be no flow of current at that point between those points and the edges containing the resistances (R1/R2 and R3/R4). Therefore, applying it to the Meter Bridge, at any such point, the galvanometer will show zero deflection.