General Question

Nimis's avatar

Why does running your cold hands under warm water seem more effective than putting them up to the heater?

Asked by Nimis (13222points) December 17th, 2008

The warming effects of running cold hands under water seem to last much longer than putting them up to the heater (even though the heater is much hotter). Or is this just me?

Does it just come down to something simple like direct contact?
I don’t think holding a warm object would have the same effect.
(ie putting your hands in warm laundry fresh from the dryer)

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6 Answers

Neurario's avatar

I imagine that it’s the same principle that you can’t feel the heat when you’re soaked in cold water. (gawd, I know what that’s like.) It probably is something to do with direct contact, but that doesn’t stop me from sitting up close to a heater.

laureth's avatar

Water is a better conductor of energy than air is.

This is the same reason that you don’t want to drop the hair dryer in the tub if you’re taking a bath, but just being in the same room with a plugged-in appliance doesn’t hurt you.

Nimis's avatar

I’d thought about that.

Obviously water is a better conductor than air.
But is that still a factor when you’re in direct contact?

Would touching the water that a dryer is submerged in
(single point of contact, not immersed in the water)
be worse than touching a live wire?

I feel like I’m missing something obvious…

laureth's avatar

I don’t think it would be worse than touching a live wire, except that there’s a larger point of contact (your whole body, not just a finger).

What I’m thinking is that the water warms your hands more efficiently, conducting more heat (energy) into your hands in the same amount of time than holding something like a warm rock or putting the hands by the heater would.

kfingerman's avatar

Think about it this way. Your body is 99ish degrees. Coldish seawater is somewhere in the 50–60 range. If you walk outside in a t-shirt and it’s 55 degrees out, you’ll be chilly – even miserable after a while – but ok. If you fell in that water, you’d be hypothermic in short order. The water conducts heat away from your body much faster than the air does. The same goes for heating your body. Another example is a hot oven. Put your hand in there, 400 degrees, crazy hot. Now touch the rack, same temp better conductor, whole different ballgame.

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