A screw gauge has a pitch of 1 mm and 100 divisions on its circular scale. When its jaws are fully closed, the zero of the circular scale is 4 divisions above the reference line. While measuring the diameter of a wire, the main scale reading is 2 mm and the circular scale reading is 45 divisions. The true diameter of the wire is:

Step-by-step solution

Least count (LC) of the screw gauge is: LC = Pitch Number of circular scale divisions LC = 1 mm 100 = 0.01 mm Since the zero of the circular scale is above the reference line when the jaws are closed, the screw gauge has a negative zero error. Zero error = -4 0.01 mm = -0.04 mm The observed reading for the wire's diameter is: Observed Reading = MSR + ( CSR LC ) Observed Reading = 2 mm + (45 0.01 mm ) = 2.45 mm The true reading is obtained by subtracting the zero error from the observed reading: True Reading = Obser