Measuring the Young’s Modulus of a Metal Thread by the Use of Tension Method

1. Measuring the Young’s Modulus of a Metal Thread by the Use of Tension Method 11#2008 Science College

2. AIM • To measure the Young's Modulus of metal wire • To know principle of blowing up of light level system • To know how to use stepwise difference

3. THEORY Young‘s Modulus (E) is a important physical quantity to describe the ability of solid material to resist deformation which is produced by outside force. E= (F/S) /(∆L/L) E ─ Young's Modulus F/S ─ Stress ∆L/L ─ Change F、S、L easy to measure ∆L difficult to measure ,we use light level system light level system theory :to use optics blowing up method to measure small change

4. THEORY • FOMULA

5. THEORY • Theory of blowing up of light level system Measuring apparatus has two parts：one is light level system and staff gauge，the other is the telescope team. When we can see n0 in the telescope and the metal wire has been drew up ∆L , the reflector deflexion ，then we see n1 in the telescope, let ∆n=n1-n0，∆n is zoom of ∆L.

6. THEORY

7. INSTRUMENT Telescope team Young's Modulus measuring apparatus

8. INSTRUMENT • Young's Modulus measuring apparatus

9. INSTRUMENT • Telescope team

10. INSTRUMENT • micrometer • tape line 5.738mm

11. A) Accommodate the Young's Modulus measuring apparatus Use your eyes to see along the two posts on the telescope to see the mirror of the light level system until you can see both the telescope lens and the mirror beside the telescope are in the mirror of the light level system completely. To realize it you should adjust position and height of the telescope team. Adjust angle and direction of the mirror beside the telescope until you can see the image of the staff gauge in the mirror of the light level system. To realize it you should turn the mirror left or right and use the bolt behind the mirror. See in the telescope in the direction of the light level system until you can see the image of the staff gauge. To realize it you should turn the telescope left or right , use the bolt under the telescope and adjust focus knob on the side of the telescope. CONTENT AND STEP

12. CONTENT AND STEP • B) Note data Press the on-off beside the screen of the Young's Modulus measuring apparatus to see 0.000,then use the black knob until the force is 14.000kg. Make sure you can see cross hairs in the telescope and confirm one horizontal line as datum line to note data. Then add to 15.000kg to note another datum until add to 23.000kg. Then do the same from 23.000kg to 14.000kg.

14. CONTENT AND STEP • C) Diameter Use micrometer to measure the diameter of metal wire , you must measure six times in three section of the wire and in each section you should use the micrometer vertically. File in the blacks. • D) D, L, b Use tape line to measure D, L, b D: from back of the staff gauge to the mirror beside the telescope L: the length of metal wire you can see b: press the light level system on a paper to get three points ,this three points can form a isoceles triangle and the height of the triangle is b File in the blacks. And finish others.

15. = mm ∆i1=0.005mm ∆i2=0.5mm F=5kg ∆F= 0.01kg

16. NOTICE • To read zero correct value ； • To read two times on the same location of staff gauge； • To the best of our abilities to do not move. If change happens, we need to renew; • Do not touch the surface of optics instruments.