A.C.Bridges

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Alternating current bridges….it’s applications and various perspectives revealed….. ALTERNATING CURRENT BRIDGES:-
INTRODUCTION:-
A bridge circuit is a type of electrical circuit in which two circuit branches (usually in parallel with each other) are "bridged" by a third branch connected between the first two branches at some intermediate point along them. The bridge was originally developed for laboratory measurement purposes and one of the intermediate bridging points is often adjustable when so used. Bridge circuits now find many applications, both linear and non-linear, including in instrumentation, filtering and power conversion. •AC Bridges, as the name suggests are alternating current bridges operates in alternating current supply. •It is used to measure:-

resistance
Inductance
Capacitance
Frequency

ACKNOWLEDGEMENT:-
The main objective of this presentation is to obtain first-hand knowledge on how AC BRIDGES works and how it can be applied to the main work field and also to prove its main impact in the field of Engineering and Technology.

It is my heartiest gratitude to respected MR.A.K.GHOSHAL, my faculty and guide through-out this project work for his professional guidance, advice, motivation, endurance and encouragements during his supervision period. The present work would have never been possible without his vital supports and valuable assistance.

Needless to mention that he has rendered his whole -hearted support and help to make this project a success. •It is only because of him and my all-out effort that we could draw up to this extent in such a field of excellence in the present days of Science and Technology.

CONTENTS:
Acknowledgement
Introduction
What is A.C Bridge??
Generalized bridge
BALANCE EQUATION
MAXWELL INDUCTANCE BRIDGE
MAXWELL INDUCTANCE CAPACITANCE BRIDGE
HAY’S BRIDGE
ANDERSON’S BRIDGE
OWEN’S BRIDGE
DESAUTY’S BRIDGE
MODIFIED DESAUTY’S BRIDGE
SCHERING BRIDGE
HIGH VOLTAGE SCHERING BRIDGE
HEAVISIDE MUTUAL INDUCTANCE BRIDGE
HEAVISIDE CAMPBELL EQUAL RATIO BRIDGE
CAREY FOSTER’S BRIDGE
CAMPBELL BRIDGE
WEIN’S BRIDGE
WEIN’ SERIES BRIDGE
WEIN’S PARALLEL BRIDGE
Bibliograpy
A balanced bridge shows a “null” or minimum reading, on the indicator. Any one of the four resistors in the above bridge can be the resistor of unknown value, and its value can be determined by a ratio of the other three, which are “calibrated,” or whose resistances are known to a precise degree. When the bridge is in a balanced condition (zero voltage as indicated by the null detector), the ratio works out to be this:

One of the advantages of using a bridge circuit to measure resistance is that the voltage of the power source is irrelevant. Practically speaking, the higher the supply voltage, the easier it is to detect a condition of imbalance between the four resistors with the null detector, and thus the more sensitive it will be. A greater supply voltage leads to the possibility of increased measurement precision. However, there will be no fundamental error introduced as a result of a lesser or greater power supply voltage unlike other types of resistance measurement schemes. Impedance bridges work the same, only the balance equation is with complex quantities, as both magnitude and phase across the components of the two dividers must be equal in order for the null detector to indicate “zero.” The null detector, of course, must be a device capable of detecting very small AC voltages. An oscilloscope is often used for this, although very sensitive electromechanical meter movements and even headphones (small speakers) may be used if the source frequency is within audio range.

APPLICATION OF ALTERNATING CURRENT BRIDGES:-

Alternating current bridges find varied application in the field of science and technology. A.C. bridges are used to measure various parameters.

MEASYREMENT OF SELF INDUCTANCES:

MAXWELL INDUCTANCE BRIDGE...
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