6 ms·
Someone asked me once if the resistor was really needed as a circuit element. I postulated that it was not desired, nor needed for any circuit that didn’t inte
by madengr 8y ago
Someone asked me once if the resistor was really needed as a circuit element. I postulated that it was not desired, nor needed for any circuit that didn’t intend to waste energy.
- CamperBob2 8y agoAlso, who needs brakes? They only slow you down!
- jacquesm 8y agoJake Brake (compression braking), regenerative braking. Those slow you down as well but do not use friction as the main working component.
- ncmncm 8y agoMotion in, heat out, either way. Regenerative braking is motion in, electrical power out. It is really just generation applied for reducing motion, but the power could as well be turned directly into heat if all you wanted was to avoid using up your brake shoes. There is a third method, where you shift down and rely on friction in your engine block to heat up your oil, and indirectly the water jacket, and dump the excess heat to the radiator.
- jacquesm 8y agoEngine braking actually supplies the engine with less fuel than is required to maintain the current speed, the engine then compresses the inlet air and releases the compressed air to the outside, this is the main element, the ones you listed are side effects of a much smaller magnitude.
- ncmncm 8y agoYou do understand that the air comes out hotter than it went in, right? And that the added heat came from the kinetic energy of the truck?
- jacquesm 8y agoYes I do. In the end it is all converted to heat and lost to the environment. The only question is when, not if. Even regenerative braking is postponing the inevitable.
- gmueckl 8y agoI will bite and counter that resistors are needed to prevent wasting energy. Current limiting resistors are used in many different places like low power electronics (these are always very high resistance) and drivers for electric motors (a powered electric motor blocked at rest is the same as a short circuit).
- madengr 8y agoThough you can do the same current limiting with a pulse width modulated switch (similar to a switching power supply). My point being you can take a resistive element and replace it with a switched transistor. All ideally of course, since it’s not practical many times.
- magicalhippo 8y agoHow would you make a constant-current power supply without resistors?
- foldr 8y agoAny practical circuit has lots of implicit resistors of very high value (between any two unconnected points on the schematic).