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Physics/Hybrid Vehicle Efficiency


How does a hybrid vehicle achieve higher MPG than a direct drive one if both are powered by internal combustion engines?  A hybrid converts the mechanical energy from the engine to electric energy, stores it in the battery, and then converts it back to mechanical energy via DC motors to propel the vehicle. Conversely a non-hybrid's power train transmits the engine's mechanical energy directly to the wheels via the drive train.  I understand there is some energy loss in the transmission, but how is converting mechanical energy to electric back to mechanical more efficient?  Is there not an inherent loss (heat, light) any time energy is converted from one form to another?

You're forgetting that hybrids only work that way on the highway, where they operate with smaller, more efficient engines.  In the city, in general, they convert a lot of the energy used to charge the battery from the brakes.  In a normal car, that's energy lost to friction as they speed up and slow down between stop lights and stop signs.


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Dr. Stephen O. Nelson


I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.


I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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