A hardware store sells a premium cordless drill. The box says its motor was re-engineered to cut waste.
Could enough re-engineering take a motor's efficiency all the way to 100%?
100% efficient would mean every joule of input becomes useful output, with nothing wasted.
No device manages that. Some of the input always ends up in the surroundings, usually as heat.
Even a well-designed electric motor delivers less useful work than the electrical energy it takes in.
Better design moves an efficiency closer to 100%. It never arrives.
So 92% efficient is possible. 100% efficient is not, for any real device.
Q: An LED bulb is measured at 90% efficiency, far above older bulbs. Could a future bulb reach 100%?
100% would mean every joule of input becomes light, with nothing wasted.
Some of the input always ends up in the surroundings, usually as heat.
The efficiency of a real device is always below 100%.
No. A future bulb can get closer to 100%, but a real device's efficiency is always below 100%.
Q: An ad says a winch takes in 700 J and delivers all 700 J as useful work. Judge the ad.
All 700 J out as useful work would mean an efficiency of 100%.
A real device's efficiency is always below 100%.
Some of the 700 J must leave as wasted output instead.
The ad cannot be right: a real winch delivers less useful work than the 700 J it takes in.
Which efficiency is possible for a real electric motor?
Mirek says: 'However well a treadmill's motor is built, its efficiency stays below 100%.' Is he correct?
Odessa says: 'A perfectly built motor, with flawless parts and the best materials, can reach 100% efficiency.' Is she correct?
Which statement about efficiency is correct?
Four motors are advertised with these efficiencies: 65%, 89%, 97%, 100%. Which advertised efficiency is impossible for a real motor?
Why is a real device's efficiency always below 100%?