Warming and lighting

warming mechanically, by rubbing

Rub your hands together, to warm them. Still you can trade-off force for distance to warm.

Press the hands together hard, and rub a little, or press together gently, and rub a lot.

Warming electrically, using an electrical loop

Some ski-gloves warm your hands electrically. There is a trade-off here as well, chosen by the manufacturer, between current and voltage.

This trade-off is linked to the understanding of electrical loops developed by the rope loop model.

Choosing a trade-offs to effect a change is available all over the place.

There is even a trade-off in designing chemical hand warmers: between the choice of chemical and the quantity of chemical.

Lighting electrically, using an electrical loop

Bulbs are designed to glow, lighting the surroundings. How much they glow depends on the voltage and the current. This is not surprising, as glowing is a kind of warming.