Young's modulus of a copper wire RQP

Method, vocabulary, apparatus and safety notes for A-level determination of the Young modulus by a simple method required practical.

Outline apparatus for the simple method.

• G clamp

• Wooden blocks x2

• Copper wire

• pointer/marker

• pulley and clamp

• 100g weights and hook

• metre ruler

• micrometer

• bench/table

Outline a method (for the simple method)

• Measure the diameter of the copper wire used. Take repeat readings and find an average.

• Set up apparatus with copper wire secured to wooden blocks on bench with a G-clamp.

• The wire must be pulled taught over a pulley with no mass on it.

• Measure the original length of the copper wire. Take repeat readings and find an average.

• Mark a reference point with tape on the ruler, preferably at the beginning of the ruler scale.

• Record initial reading of this reference point

• Add 100g mass onto the hook

• Read and record new reading of tape marker

• Repeat method, adding 100g mass each time

• Record total mass, load and extension in a table.

Safety hazards

• Masses falling and damaging the floor or falling on someone

• Copper wire breaking and injuring someone

What are the units of Young Modulus?

Pascals

Label the divisions of the micrometer and their scale.

• each big division is 1mm (0.1cm), the halfway lines are 0.5mm

• on the right, each division is 0.01mm (therefore 40 = 0.4mm)

How to find the Young Modulus of a copper wire from a graph?

• Calculate stress and strain for each set of readings.

• Plot a graph of stress/strain

• Gradient is young modulus.

Risks

• Injured foot or leg

• Blindness, cuts on body or damaged clothes.

Mitigation for risks and safety hazards.

• Wear safety goggles

• Keep clear of area when weights are being dropped

• Add cardboard boxes to prevent floor from being damaged

• Mark out area to keep clear from if weights fall