The micrometer screw gauge consist of a thimble which carries a circular rotating scale known as thimble scale and a spindle which moves forward and backwards when the thimble is rotated.It is used to measure very small lengths such as the diameter of a thin wire.State the correct reading of the scale if the instrument has a zero error of –0.02cm. The figure below shows a vernier callipers The negative error is corrected by adding zero error to the reading obtained.This vernier callipers has a negative error of -0.02 cm Occurs when the zero mark of the main scale is to the right of the zero mark of the vernier scale.The positive error is corrected by subtracting the zero error from the reading obtained.This vernier callipers has a zero error of +0.13cm Occurs when the zero mark of the main scale is to the left of the zero mark of the vernier scale.Vernier callipers is said to have a zero error if the zero marks of the main scale and vernier scale do not coincide when the jaws of the calipers are closed without an object.Write down the vernier calipers reading in diagram (a)(b) and (c) showed below.Describe how you would measure the internal diameter of 100cm 3 beaker using vernier callipers.Vernier Callipers reading = Main scale reading + Vernier scale reading: = 10.0 cm + 0.02 cm = 10.02 cm Exercise Vernier scale reading: 0.02 cm (Alignment of scale lines) Vernier callipers reading = vernier scale reading + main scale reading The sum of the vernier scale reading and the main scale reading gives the diameter(length) of the object.Read the vernier scale mark that coincides exactly with a main scale mark and multiply it with the least count(accuracy) of the Vernier callipers.Record the reading of the main scale, opposite and to the left of the zero mark of the vernier scale.Close the jaws till they just grip the object.Place the object whose diameter(length) is to be measured between the outside jaws.Vernier callipers has inside jaws used to measure internal diameters and outside jaws used to measure external diameters.This is the accuracy of the Vernier callipers i.e. The difference between the main scale division and the Vernier scale division is called the least count.The length of Vernier scale is 0.9cm implying that each division of the vernier scale is 0.09cm.The Vernier scale is contained on the sliding jaw and has 10 equal divisions. The Vernier callipers has two scales.The main scale is contained on the steel frame and is graduated in centimeters but also has millimeters divisions.Possible Sources of Error in the Experiment.Assumptions Made in Oil Drop Experiment.The Zero Error of the Micrometer Screwgauge.