Let’s make a foam
cutter! First you need to understand that Styrofoam (polystyrene)
vaporizes at certain temperature. A foam cutter, is nothing but a hot wire that
pass through foam
like a hot knife through butter. How to heat a wire?
Simplest way: connect a wire to the positive of a battery and the other end to the negative
of a battery.
This is extremely dangerous. The wire will become so hot that the wire itself might melt!
You will be burnt if you hold it! Its insulation will melt! Depending on what is around, you
can start a fire. Safer method is to use nichrome wire - or high resistance wire as some
colloquially call it. Now to understand why it is safer, you need to understand why a wire
A wire has resistance. And resistance’s job is to convert electrical energy to heat energy.
Nichrome wire has a lot of resistance compared to copper wire. So if you connect your battery
using low resistance
wire (e.g. copper wire you find in almost all wires around the house) to a nichrome wire -
since the nichrome wire has more resistance, all the heat conversion happens there and your
low resistance copper wire does not heat up.