Science 10. Aim: Efficiency , Energy and us. Agenda. Efficiency, Energy and us Study Guide – Homework Quizzes back on Monday Next class. Useful Energy and Efficiency. The initial energy source applied to a machine is called the energy input (think electricity)
Car engine efficiency = 12-15%
Electric engine = Up to 95%
Steam reciprocal engine = 50-75%
Steam turbine engine = Up to 40%
In heating a pot of water, 2.00x103 J of heat was supplied by the stove element. If only 5.00x102 J of heat was actually gained by the water (heat output), what was the percent efficiency of the stove element?
For devices that convert heat to mechanical energy use
For devices that convert mechanical energy to heat use
Energy supply broken down into two types
Renewable and Non-renewable Energy sources
Historically, our ancestors used only renewable resources like solar energy wood or biomass.
This is only a fraction of what is used today.
There is a high demand placed on energy sources now.
At the rate we are using oil, coal, and natural gas, it is projected that our supply will run out in ~40, ~216, and ~62 years respectively.