Measuring Young Modulus

Measuring the Young modulus of a material in the laboratory requires careful experimental technique. The challenge is that metals are very stiff — even under substantial loads, the extension of a wire might be only a fraction of a millimetre. Accurate results demand precise measurements and a systematic approach to minimising uncertainty.

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The Long Wire Method

The standard A-level experiment uses a long, thin wire under tension. A long wire is used because extension is proportional to original length (ΔL = FL/AE), so a longer wire gives a larger, more measurable extension for the same stress.

Apparatus

• A length of wire (typically copper or steel), at least 2–3 metres long
• A clamp or fixed support at one end
• A pulley at the free end with a weight hanger and slotted masses
• A ruler or metre rule to measure the original length
• A micrometer screw gauge to measure the wire diameter
• A travelling microscope or marker and ruler system to measure extension
• Safety goggles (the wire may snap under high loads)

Setup