Safety Warnings
The variac outputs high voltage (up to 140V) and the wire draws significant current (4A). Ensure all connections are secure before applying power. Do not touch any electrical connections while powered. The variac and apparatus should be on an insulated surface.
The nichrome wire becomes extremely hot during operation (potentially several hundred degrees Celsius). Do not touch the wire or apparatus frame near the wire during or immediately after the demonstration. Allow at least 10 minutes for cooling before handling. The wire will glow visibly when hot.
Purpose
A nichrome wire heated by electrical current visibly expands, moving a pointer across a calibrated scale. Students observe thermal expansion directly and see that even small length changes become measurable with mechanical amplification.
