EXPERIMENT NO.2
Anderson’s bridge
AIM OF THE EXPERIMENT:

To measure the self inductance of a given coil by
Anderson’s bridge method.
APPARATUS USED:

Inductor,standard capacitor,resistors( fixed
resistances and variable pots as given in the
circuit) signal generator,headphones and
connecting terminals.
FORMULA USED:

Inductance of given coil L=RC(Q+2r) mh
DESCRIPTION:

Anderson’s bridge is the most accurate bridge used for the
measurement of self inductance over a wide range of values from a
few micro-henries to several Henries.In this method the unknown selfinductance is measured in terms of known known capacitance and
resistances,by comparision.It is a modification of Maxwell’s L-C
bridge.In this bridge,double balance is obtained by the variation of
resistances only,the value value of capacitance being fixed.
PROCEDURE:

The circuit diagram of the bridge is as shown in the figure.The coil whose
self-inductance is to be determined,is connected in the arm AB,in series
with a variable non-inductive resistor R1. Arm BC,BD and DA contain fixed
and non-inductive resistors R2,R3 and R4 respectively.Another non-inductive
resistor R5 is connected in series with a standard capacitor C and this
combination is put in parallel with the arm CD .The head-phones are
connected between B and E. The signal generator is connected in between A
and C junctions. Select one capacitor and one inductor and connect them in
appropriate places using patch chords.The signal generator frequency is
adjusted to audible range.A perfect balance is obtained by adjusting R1 and
R5 alternatively till the head-phones indicate a minimum sound . The values
of R1 and R5 are measured with a multi-meter (While measuring the R1and R5
values,they should be in open circuit).In the balance condition, the self
inductance value of the coil is calculated by using the above formula.The
experiment is repeated with different values of C
DIAGRAM OF THE EXPERIMENT:
OBSERVATION:

For a.c circuit:
Sl no
For L1
1
2
For L2
1
2
For L3
1
2
Capacity(C) µF
Resistance
R1(Ω)
Resistance
R5(Ω)
Calculated
valued of L
L=RC(Q+2r)
0.2
0.1
42
42
2500
5500
0.0504 h
0.0504 h
0.1
0.2
44
44
11,100
4540
0.10208 h
0.088704 h
0.2
0.1
45
45
8100
11,100
0.1044 h
0.1044 h

For d.c
S.no
Capacity(C)
Resistance R1
(Ω)
Calculated
value of
L=RC(Q+2r)
Resistance R5
(Ω)
0.1
0.2
42
42
0.0252 h
0.0462 h
1000
5000
2
0.1
0.2
48
48
0.0111 h
0.0222 h
11,100
11,100
FOR L 3
1
2
0.1
0.2
110
110
0.0255 h
0.0510 h
11,100
11,100
FOR L1
1
2
FOR L2
1
PRECAUTIONS:

1) THE PRODUCT (CR2R4) MUST ALWAYS BE LESS THAN L.

2) R1 AND R5 ARE ADJUSTED UNTIL A MINIMUM SOUND IS
HEARD IN HEAD-PHONES.
CONCLUSION:

THE VALUE OF L1,L2 AND L3 ARE FOUND OUT TO BE 0.0504
h,0.0953 h AND 0.1044 h RESPECTIVELY