ENERGY & EFFICIENCY

EFFICIENCY When energy is transferred from one form to another … No energy is destroyed. Some of the energy is converted to a form of energy that is not useful.

EFFICIENCY Ranking based on a percentage that tells us how complete an energy transfer was. The ratio, expressed as a percentage, of the useful energy provided by a device to the energy required to operate the device.

Efficiency

EFFICIENCY A machine will convert one type of energy into another type of energy. Eout is what energy you get out of the machine you are using. It is the smaller number. Ein is what you have to put into the machine to make it work. It is the bigger number. Example A light bulb takes in electrical energy (Ein) and converts it to radiant energy (Eout).

EXAMPLE 1 A firefly’s body transforms chemical energy in food into radiant energy that appears as a greenish glow in its abdomen. Fireflies use this glow to attract mates or prey. What is a firefly’s efficiency if its body transforms 4.13J of chemical energy into 3.63J of radiant energy?

EXAMPLE 2 A family uses several planks to slide a 350-kg piano onto the back of a pickup truck. The box on the back of the truck is 81 cm above the ground and the planks are 3.0 m long. An average force of magnitude 1500 N is required to slide the piano up the planks. Determine the work done in loading the piano. Calculate the “useful work”. Calculate the efficiency of the planks as a simple machine to load the piano. Where does the rest of the energy go?

EXAMPLE 3 A construction worker uses a rope and pulley system to raise a 27-kg can of paint 3.1 m to the top of a scaffold. The downward force on the rope is 3.1 × 102 N as the rope is pulled 3.1 m. Find the work done in raising the can of paint. How much “useful work” is done? What is the efficiency of the rope and pulley in raising the can of paint? Suggest why the efficiency of this simple machine is not 100%.

ENERGY RESOURCES Where does our energy come from?

ENERGY RESOURCES Where does our energy come from? RENEWABLE RESOURCES -solar energy -wind energy & tidal wave energy -hydroelectric -geothermal

Solar Energy

Tidal Energy

Wind Energy

Hydroelectric

Geothermal Heating

ENERGY RESOURCES Where does our energy come from? NON RENEWABLE RESOURCES Fossil Fuels Nuclear Energy -coal (mining) -fission of -oil (rigs/wells) radioactive uranium -natural gas (fracking)

Nuclear Energy

Fossil Fuels Oil, Coal, Natural Gas

Natural Gas (methane) Fracking

Fracking Has been in the news recently Opposition to fracking in NB http://www.youtube.com/watch?v=dEB_Wwe-uBM