Burning wood with a hot wire is a classic. I tried a new version, with a steel wire sandwiched between two pieces of wood and the subjected to 12 V from a car battery.

The 1.6 mm mild steel wire of about 50 cm have a resistance of about 0.05 Ohm. That translates to a current of about 240 A with a 12 V car battery. Enough to make the wire hot in an instant.