Sometimes it’s nice for those of us with bad backs or muscle aches to have a heated seat.
This is common in cars, so today’s invention extends the idea to one’s house.
You could, of course, just insert an electric blanket into an armchair and plug it in.
This might easily become unsafe after repeated use, however.
Imagine instead that the armchair is fitted with two large copper plates, one for the back and one for the seat. These would be connected by some very fat, insulated copper cables to any nearby radiator and clamped to the hot surface.
Over time, the seat becomes pleasantly warm, with no risk of fire or electrocution.