If the wire snaps, the same hazards would take place as mentioned above but, the weight dropping to the floor will cause damage to the toes etc, if the weight falls on the foot, so keep a safe distance as soon as the extra load is added. DO NOT ADD THE WEIGHTS QUICKLY AS THE WIRE IS SENSITIVE WHEN THERE IS ALREADY A LARGE FORCE APPLIED ON IT. The vernier scale is sensitive, so we have to pay particular attention to how much force we apply, because the maximum extension, which can be read, depends on the size of the scale.
Due to the increase in the average cross-sectional area, which affects the extension in the wire, we need to increase the accuracy of the readings by taking repeats, using different wire of the same diameter, and again take measurements of the diameter, with use of the micrometer. This increases the reliability of the results and hence the Youngs modulus of the copper wire. The vernier scale method is much more accurate than the clamp and pulley method, which could have been used as well, but as we are aiming for accuracy it is best to use the vernier scale method.
The experiment is to be conducted under room temperature, because the temperature of the wire whether cold or hot reduces the accuracy of the results, the wire stretches more under warm conditions because the wire is less stiff than if it was in cold or even room temperature of 23 oC. I will have to take account of possible errors, such as the zero error in equipment, and other random and systematic errors, which can occur. I will try to avoid making the parallax errors, (the error which occurs when the eye is not placed directly opposite a scale when a reading is being taken).
This can be made on reading off a ruler. The reading errors (the error due to the guess work involved in taking a reading from a scale when reading lies between the scale divisions, and the zero error (the error which occurs when a measuring instrument does not indicate zero when it should), which can be possible on the vernier scale. If the zero error happens, then I will adjust the instrument to read zero or the inaccurate zero reading should be taken and should be added or subtracted from any other reading taken. Sometimes the metre rules have worn edges and so I will measure from 10cm instead of 0cm.
As the wire is stretched, the diameter of the copper wire decreases, we get plastic deformation before it snaps, for example if we look at a copper rod as a large scale to the thin wire you can see from the below that the copper rod necked before it broke. This happens because metals like copper, (above) are ductile- they can have large plastic deformations without fracturing. It happens because atoms move, as the plastic deformation in the crystal structure move, to place of lower stress. The copper becomes thinner when atoms move away from the stressed part.
The stress then increases because the cross-sectional area is now decreased. This increases the ductile flow and so the metal yields and gets thinner and thinner. Once plastic deformation starts, atoms will continue to flow without any increase in stress. This stretching under a constant load is called creep. The thinning of a wire/rod is called necking. There is also the problem that the kg masses may not weigh the given value, there is a small chance that this would be inaccurate, the only way to find out is by weighing the mass using a electronic scale, which is accurate to 0. 001g.
Physics For You By Keith Johnson Dictionary of Science By C. Stockley Simmone Hewett C. Oxlade Sue Holt J. Weitheim John Miller Physics 1 By David Sang Keith Gibbs Robert Hutchings Science Desk Reference By Patricia barnes-Svarney www. s-cool. co. uk www. allmeasures. com Encarta 2002 AS Physics Assessed Practical (Skill P) Elasticity of a Copper wire By Priyesh Patel 12O 1 Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.