© Javaid Khurshid, PIEAS Page

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Experiment : M

ELDE

’

S

E

XPERIMENT

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:

Sonometer

Procedure:

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.

L

M

(resourcefulphysics.org)

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© Javaid Khurshid, PIEAS Page

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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 (m

o

)

xi. By putting values of l, m

o

, 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’.

Observation:

Mass of 100cm of wire = m = ---------------gm

Mass of per cm of wire = m

o

= m/100 = ----------------gm/cm

Acceleration due to gravity = g = = 980 cm/s

2

Calculations:

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

gm

Resonate length of segment

of wire between two wedges

1

cm

2

cm

Mean ‘l’

cm

1

2

3

4

5

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