To Determine the Area of Cross Section of a Thin Wire using a Screw Gauge

• Apparatus: Micrometer screw guage, piece of wire.
• Diagram
• Procedure: I found out the value of smallest scale. division on the linear scale and total no. of divisions on the circular scale (vernier scale) of noted the pitch of screw and determined the least count of 'screw guage by using the formula L.C = Pitch of screw / No.of divisions on circular scale. I determined the zero error of Screw guage by bringing the two studs together.  I placed the wire between two studs A and B and turned the screw. I read the linear scale reading "R" and noted the circular scale reading (N) facing the base line (L). I applied the zero correction and Calculated the correct diameter. 
• Result: Calculated the area of cross-section of wire by using formula: A = pi r² area of crosssection of given wire = 1.42sq.mm.
• Observations
• Calculations
• Results: Mean diameter of the wire = D = 0.408 mm
• Radius of the wire = r = D/2 = 0.408 mm = 0.204 mm
• Area of cross - section of the wire = πr² = 3.1416 x (0.204)² mm² = 0.1307 mm²
• Precautions:  Do not press the screw too hard. Remove the kinks in the wire. The zero - correction should be applied.
• Always revolve the screw in the same direction to avoid back - lash error. Take two reading perpendicular to each other at each place on the wire.
• Q: What is meant by the pitch of a screw gauge? Ans: The value of 1 smallest division on main scale is called pitch of screw gauge. Its value is 1mm.
• What happens to the temperature of the room? When an air conditioner is left running on a table in the middle of the room? Ans: The temperature of the room increases slightly. Reason: - When an air conditioned is left running on a table in the middle of the room, it absorbs as well as reject heat in the same room at the constant rate. So, the temperature of room is unchanged. But due to the working of compressor some heat is produced due to friction which increases the temperature of the room slightly. 11. Can the mechanical energy be converted completely into heat energy? If so give an example. Ans: Yes, mechanical energy can be converted completely into heat energy. Example: - When brakes are applied to stop the running car, then the car stops due to friction and all the mechanical energy supplied to the car is converted into heat due to friction. Also, during isothermal compression then work done on the system is converted into heat energy. Q = ΔU + W ΔU = 0 (For inothermal Process) Q = W, W = Q 
• Q: What is meant by least count? Ans: The minimum measurement which can be made by the instrument is called its Least count.
• Q: If pitch of the screw is 1 mm and the number of divisions on circular scale is 100 then find the least count of the screw gauge?Ans: Lease count = Pitch of the screw No of divisions on the circular scale h1 N 100 = 0.01mm
• Q: What is the use of a screw gauge? Ans: It can be used to measure the diameter of a thin wire or a small sphere.