Physics Lab

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Measurement of the distance, the thickness and the radius of curvature Purpose :
To learn how to use vernier caliper, micrometer and spherometer to measure internal and external diameters of a pipe,the thickness of a copper rods, and the radius of curvature of spherical lenses. 1) Vernier caliper: As shown in Fig. 1 the main fixed scale in the vernier caliper has 1 mm gradations while th sliding scale (vernier scale) has 0.05 mm gradations. The smallest division of vernier scale is called the least count of vernier caliper. It may be different for different vernier calipers (and other measuring instruments).

In order to measure length, put an object between the jaws and close the jaws gently. Fix the object with the fixing screw.

(Fig.2b)

In Fig. 2b, the leftmost thick mark on the sliding scale is between 9 mm and 10 mm, so the number of whole millimeters is 9. And number 3 on the vernier scale matches exactly with a mark on the main scale, so the caliper reading is 9+(3x0.05), which equals to 9.15 mm.

When we want to measure external diameter, you use outside jaws, and for internal diameter and depth, we use inside jaws and depth probe, respectively.

2) Micrometer:

(Fig.3 Schematic view of a micrometer)

* Frame
* Anvil
* Spindle
* inside sleeve
* outside sleeve
* lock nut
* thimble
* ratchet stop
* ratchet screw
* spindle lock
* frame cover
* carbide tip

The spindle of an ordinary metric micrometer has 2 threads per millimeter, and thus one complete revolution moves the spindle through a distance of 0.5millimeter. The longitudinal line on the inside sleeve is graduate with 1 millimeter divisions and 0.5 millimeter subdivisions. The thimble has 50 graduations, each being 0.01 millimeter (one-hundredth of a millimeter). Outside sleeve indicates 12.5 mm, and longitudinal line on the inside...
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