A micrometer screw gauge is used to measure the diameter of a copper wire. The reading with the wire in position is shown in diagram 1. The wire is removed and the jaws of the micrometer are closed. The new reading is shown in diagram 2. -15 20 10 -15 5 10 diagram 1 diagram 2 What is the diameter of the wire? A 1.90 mm B 2.45 mm C 2.59 mm D 2.73 mm LO

Note: It is important to identify that the micrometer in diagram 2 shows a positive zero error. Therefore, the value of the error must be subtracted from the reading shown in diagram 1 in order to obtain the diameter of the wire. Choice B is correct because: Obtain the micrometer reading for the diameter (diagram 1) Micrometer reading = Main scale reading + Micrometer scale reading Micrometer reading = 2.5 mm + 0.09 mm = 2.59 mm [Note: Micrometer scale readings are taken in terms of millimetres (mm)] Subtract the zero error from the diameter reading to calculate the final diameter reading Diameter of wire = 2.59 mm - (+0.14 mm) Diameter of wire = 2.45 mm Choices A, C & D are incorrect because they do not correctly state the diameter of the wire as 2.45 mm.

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Micrometer Screw Gauge | 2010 - M/J - 9702/11 | Q7