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Andersons bridge

Aim : -

To measure the self - inductance of a given coil by Andersons bridge method.

Apparatus :- Inductor, standard capacitor, resistors ( ed resistances and variable

pots as given in the circuit ! signal generator, head phones and connecting

terminals.

"ormula :-

Inductance of given coil # $ % & ( ') '* ! '+ ) '*' m /here % $ %apacity ofthe standard capacitor ( 0 " ! '*,'1,' $ 2no3n, ed and non 4 inductive

resistances (25! ', '+ $ 6ariable resistances ( 25 !

7escription :-

Andersons bridge is the most accurate bridge used for the measurement of self 4

inductance over a 3ide range of values, from a fe3 micro-enries to several

enries. In this method the un8no3n self-inductance is measured in terms of 8no3n

capacitance and resistances, by comparison. It is a modication of 9a3ells # - %

bridge. In this bridge, double balance is obtained by the variation of resistances

only, the value of capacitance being ed.

rocedure :-

The circuit diagram of the bridge is as sho3n in the gure. The coil 3hose self-

inductance is to be determined, is connected in the arm A;, in series 3ith a variable

non-inductive resistor '. Arms ;%, %7 and 7A contain ed and non 4 inductive

resistors '*, '1 and ' respectively. Another non - inductive resistor '+ is

connected in series 3ith a standard capacitor % and this combination is put in

parallel 3ith the arm %7. The head - phones are connected bet3een ; and elect one capacitor and

one inductor and connect them in appropriate places using patch chords. The signal

generator fre?uency is ad=usted to audible range. A perfect age * of 1 balance is

obtained by ad=usting ' and '+ alternatively till the head 4 phones indicate a

minimum sound. The values of ' and '+ are measured 3ith a multi-meter( /hile

measuring the ' and '+ values, they should be in open circuit !.In the balance

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condition the self 4 inductance value of the coil is calculated by using the above

formula. The eperiment is repeated 3ith di@erent values of %.

recautions : -

! The product (%'*'! must al3ays be less than # . *! ' and '+ are ad=usted

until a minimum sound is heard in head 4 phones.

'esult :- age 1 of 1 Table >.o. %apacity ( % ! 0 " 'esistance ( ' ! 5 'esistance

( '+ ! 5 %alculated value (#! % & ( ') '* ! '+ )'*' m >tandard value of # m

. *. 1. . +. B. C C C C C