Determine Young’s modulus of elasticity of a wire by ratus:

Apparatus :

Scarle’s apparatus, micrometers screw gauge, meter rod, two identical wires, and spirit level and kilogram weights.

Observations:

Length of wire (L)                                           = ……Cms

Pitch of the screw gauge                               =……mm

Number of division on circular scale            =……mm

Least count of the screw gauge                    =……mm

Zero error in the screw gauge                       =……mm =…..cm

Mean zero error                                              = (i)….mm (ii) ….mm (iii) ……mm

Zero correction for screw gauge                  =……….mm

Diameter of the wire                                      =………..mm

Mean observed diameter of the wire           = (i)……mm (ii) …… (iii) …..mm

Radius of wire  (r)                                         =………..mm

Breaking stress for the material of wire from the table    =kg.wt/sq.cm.

Maximum load to be applied                      =….mm=………..cm

Maximum load to be applied                        =kg.wt.

Micrometer……………………………………. =…..mm=………cm

Least count of the micro meter             =……..mm=………cm

Extenstion for 2 kg.wt	Mean	Micrometer reading of circular scale On loading  On unloading	AdditionalLoad in kg.wt	No.of Obs
				123456

Calculation:

Mean extenstion for 2 kg.wt =               =mm

Force                                      =2 kg.wt         =2100981 dynes

Stress                        

Longitudinal strain                           =l/L

Young’s modulus (Y) =stress /longitudinal strain =FL/(al)

Percentage error                 =           %

Procedure:

First suspend two identical metal wires EF & GK from the same rigid support. Attach the lower end of the wire EF to the frame R and that of second wire GK to the frame P. Han heavy load, “W” with the frame P, heavy enough to keep the wire GK in a stretch state Measure the length ‘L’ of the wire from the point of suspension to the point where it is fixed to the Scarle’s apparatus. Find the diameter of the experimental wire with screw gauge at different places and calculate its area of cross-section. The frame R, will be depressed relative to frame P, due to hanger ‘H.’ Rotate the head to the micrometer screw M, till the spirit level becomes horizontal and take the reading of screw gauge. Add more weight of 1 kg on the hanger H, the spirit level will not remain horizontal due to stretched wire. Turn the head of the screw gauge M in such a way that bubble again comes in the center of spirit level. Take new reading of the micrometer. Repeat this experiment by increasing the weight, every time by 1 kg up to 5 kg and taking the corresponding new reading after adjustment of spirit level. Unload the weight one by one from the hanger and note on readings adopting the sarne procedure. Take the mean value for each load. In order to find & for 2 kg Subtract pair to alternate readings and take their mean value using the relation and find the Young’s Modulus.

Precaution :

1. The least count of the micrometer and that of the screw gauge should be noted carefully.

The readings should be recorded both by loading and unloading the wire.2

. Wire suspended should be free from kinks and bends.3

Loading of wire should not be beyond 1/3 of its breaking stress..4

VIVA VOCE

Q.1. what is Young’s Modulus?

Ans. It is the ratio of stress to longitudinal strain

Q.2. what is the yield point?

Ans. It is limit beyond which the wire begins to flow down even in spite of the constant load?

Q.3. Define stress and strain?

Ans. Deforming force per unit area is called stress. Ratio of the change produced by the deforming force to the original length or volume or shape of a body is called the longitudinal, volume or shearing strain.