Aim and variables
The aim is to determine the Young modulus of a metal wire by measuring its extension for a range of applied forces.
| Variable | Quantity |
|---|---|
| Independent | Applied force or load, |
| Dependent | Extension of the wire, |
| Controlled | Original wire length, wire thickness and material of the wire |
Horizontal wire arrangement
The wire is fixed along the bench and runs over a pulley at its edge to a hanging mass. Increasing the hanging mass increases the tensile force in the wire.
A reference marker on the wire extends to the metre-ruler scale so its displacement can be used to calculate extension.
The pulley allows the load to hang vertically while reducing friction compared with taking the wire directly over the edge of the bench.
An alternative simple method uses a vertical wire fixed at its upper end with a load suspended below it.
Apparatus
| Apparatus | Purpose |
|---|---|
| Metal wire | Material for which is to be determined |
| G-clamp and wooden blocks | Hold the apparatus and wire securely |
| Bench pulley | Redirect the wire so a load can hang freely |
| Mass hanger and masses | Produce a controllable tensile force |
| Metre ruler and marker | Measure wire length and changes in marker position |
| Micrometer | Measure the diameter of the wire |