Nichrome Wire

The wire becomes extremely hot — do not touch during or after the demonstration. Allow 5–10 minutes cooling before handling.

Ensure all connections are secure before applying power. Do not touch connections while power is applied.

Too much current will break the wire suddenly. Increase current gradually — watch for excessive sagging or bright glow. A high enough current will end the experiment prematurely.

Purpose

Nichrome wire heated by resistive current elongates and sags into a visible catenary, demonstrating linear thermal expansion of solids. The progressive glow also illustrates blackbody radiation and connects to incandescent light bulb filament physics.

Nichrome wire stretched between two ring stands with alligator clips and power cords connected to a variac (left); four progressive shots showing the wire glowing increasingly bright and sagging into a catenary as current increases (right)

Figure 1:

Warning: High Temperature Hazard

Warning: Electrical Safety

Warning: Wire Breakage

Purpose

Safety Warnings

Warning: High Temperature Hazard

Warning: Electrical Safety

Warning: Wire Breakage

Purpose