Experiment No. Phy-6
Object:
To determine frequency of A.C. mains using sonometer.
Apparatus:
• A sonometer with a steel wire of unknown diameter.
• Electromagnet
• A step down transformer(220V to 6V or 12 V)
• Rheostat
• Hanger with slotted weights of 1Kg each
• Mete Rod
• Two wedges
Formula used:
0
1
4
Mg
f
l m
=
Sonometer
Procedure:
i. To perform this experiment usually a sonometer is used in which an
electromagnet is fitted in the middle. 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.
ii. Put suitable slotted weights in hanger so that the wire may remain
in tension without any bends or kinks
iii. Place one wedge on one side and the other wedge on other side of
electromagnet at nearly equal distances from there. Also put a
small rider of paper on the wire above the electromagnet.
iv. Switch on circuit of electromagnet. The steel wire will begin to
vibrate Adjust position of wedges by moving them slowly until the
rider flies off. Then amplitude of vibration will be maximum and
transverse stationary waves will be set up in the segment of wire
between wedges with nodes at wedges and anti-notes in the middle
(above the electromagnet.)
v. Measure length of segment of wire between wedges by meter rod
twice by repeating step (iv) and find its mean value ‘l’.
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