Wasted Energy Flashcards

All 4 cards in this deck

What makes a mechanical process wasteful?

It causes a rise in temperature, dissipating energy in heating the surroundings.

In an electric motor lifting a load, which energy transfer is useful and which is wasted?

Useful: energy transferred to the kinetic (and gravitational) store of the load. Wasted: energy dissipated to the thermal store of the surroundings by friction, plus sound.

Why is the efficiency of an engine always less than 1 (100%)?

The useful output energy is less than the input energy, because some energy is transferred to less useful forms — dissipated to the surroundings as thermal energy.

Give a reason, other than friction, why energy is wasted in a pulley system.

There is additional mass in the system (the bottom pulley and the rope have weight), or the rope stretches.