Sonometer Experiment-Physics-Lab Mannual, Exercises for Physics. Allahabad University
sateesh17 July 2012

Sonometer Experiment-Physics-Lab Mannual, Exercises for Physics. Allahabad University

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This is lab manual for Physics course. It was designed by Sakash Jashith at Allahabad University. It includes: Frquency, Sonometer, Step-down, Transformer, Hanger, Weights, Wedges, Electromagnet, Vibrations, Transverse
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© Javaid Khurshid, PIEAS Page 1 of 2


Object: To determine frequency of A.C. mains using Sonometer. Apparatus:

• A sonometer with a steel wire.

• Electromagnet

• A step down transformer(220V to 6V or 12 V)

• Hanger with slotted weights of 500g each

• Meter Rod

• Two wedges

Formula used:    



i. To perform this experiment usually a sonometer is used in which an electromagnet is fitted in the middle.

ii. Connect one end of a steel wire of uniform diameter to peg and connect other end to hanger after passing it over two wedges and a frictionless pulley.

iii. Put suitable slotted weights in hanger so that the wire may remain in tension without any bends or kinks.

iv. Place one wedge on one side and the other wedge on other side of electromagnet at nearly equal distances from centre. Also put a small rider of paper on the wire above the electromagnet.

v. Switch on circuit of electromagnet.

vi. Adjust position of wedges by moving them slowly outward until there is vibration in the wire.

vii. Adjust the wedges so that the amplitude of vibration is maximum and transverse stationary waves could be seen with nodes at wedges and anti-notes in the middle.

viii. Measure length of segment of wire between wedges by meter rod twice by repeating step (iv) and find its mean value ‘l’.

ix. Repeat step (iii) to (viii) by changing weights in hanger at least five times.




© Javaid Khurshid, PIEAS Page 2 of 2

x. Take a piece of 100cm of same steel wire .Measure its mass by physical or electronics balance and divide it by 100 to get mass of wire per cm (mo)

xi. By putting values of l, mo, M and g in formula

xii. Calculate frequency ‘f’ of A.C. supply for each set of observation and then find mean value of ‘f’.


Mass of 100cm of wire = m = ---------------gm Mass of per cm of wire = mo = m/100 = ----------------gm/cm Acceleration due to gravity = g = = 980 cm/s2


For observation 1 =     = For observation 2 =     = For observation 3 =     =

For observation 4 =     =

Mean Value of ‘f’ =

Results: Frequency of A.C. mains, experimentally found is = Actual frequency of A.C. mains = Percentage of Error =

(Experimental Value – Actual Value)* 100 / Actual Value =

Sr.# Mass Suspended with wire including mass hanger M in


Resonate length of segment of wire between two wedges

1 cm

2 cm

Mean ‘l’ cm

1 2 3 4 5