But an electric motor will draw 10 amps at 220v and it will draw 20 amps at 110v. When I cut the voltage in half I double the amps draw. I work on them and do amps tests every day for a living. Most Toughbook AC adapters say the exact same thing on them. At 120v they use 1.2a and at 240v they use .6a....
I misstated ohms law, and you are correct. When you lower the voltage, less amps will become available.
The resistance will remain constant. Therefore I believe the wattage used will also remain constant.
So 100 watts equals 15volts times 6.667amps, But 100 watts at 12volts requires 8.33 amps. So at 12volts the amperage draw will increase. This can increase heat depending upon several factors. Wire size etc..
Yeah theres more than one way to 'skin a cat'... From the point of view of DC 'electronics', without the appropriate minimum voltage and the resistance of a circuit being the same, it simply will not operate(if V too low), run(not to discount errors), or shortout(V too high).
When we are talking power adapters/converters, they are designed to change the power values, so yes a 240V adapter will use half the amperage than 120V input and the output would remain the same; In this case the internals of the adapter must be able to handle the higher amperage.
Computers have quite a number of voltage lowering internals for various components, but this is all stepped down already from the system battery or main DC power source.
With regard to Electric motors, or transformers in many 120-240V power supplies it is simply a selection(physical or digital, but ultimately physical). The motor/transformer simply has X number of windings of wire around it, power running through it. At a different voltage, a switch connects at a different position in the winding(like the 110-220V switch on back of desktop power supplies). It's still Ohmns Law.
The only risk I am aware of is in motors/compressors where the voltage is lowered to a point where it won't quite turn over and sit there consuming power generating heat burning out the motor/fire.
--- But I digress, it is generally safe in electronics to test with lower voltages; 'blindly' higher not at all!. I've taken dozens of my new toys that I could not afford to purchase again/ruin and run lower voltages through them for various reasons/trials.
Assuming no toughbook geek with a multimeter and extra DC plug w/adjustable power adapter steps in with his results for his computers, I think I will purchase one Toughbook CF-T8 just to try it myself; Would prefer rugged, but for ~$80 for the T8 and 10W tdp cpu, should be a good low power item to test.