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# Science 10 PowerPoint PPT Presentation

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)

Science 10

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### 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)

• The desired energy needed to do work is called the useful output energy

• The work done by the machine is called the useful work output

• Energy and work that is not useful are called waste energy and waste work

### Efficiency

• A measurement of how effective a machine is at converting energy input into useful energy output.

Car engine efficiency = 12-15%

Electric engine = Up to 95%

Steam reciprocal engine = 50-75%

Steam turbine engine = Up to 40%

Or

### Question

• A crane lifts a load of construction materials from the ground to the second floor of a building. In the process, the crane does 2.30 x 104 J of work or mechanical energy input, while doing 8.00 x103 J of useful work or mechanical energy output in lifting the load. What is the mechanical percent efficiency of the crane?

### Transfer of total thermal energy to useful thermal energy

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?

### Conversion of total thermal energy to useful mechanical energy or vice versa

For devices that convert heat to mechanical energy use

For devices that convert mechanical energy to heat use

### Energy Applications

Energy supply broken down into two types

• Solar energy sources

• Non-solar energy sources

Renewable and Non-renewable Energy sources

• Renewable – Continually and infinitely available.

• Non-renewable – limited an irreplaceable

### Energy Demand

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.

• Amount of energy used per person has increased exponentially

• The world population has increased as well.

• Many societies use non-renewable resources rather than renewable resources.

### The effects of energy use

• The high demands of fossil fuels has led to a strain on existing supplies

• Searching for and extracting new supplies have led to damaging effects on the ecosystem.

### Energy Consumption and Conservation

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.

• Decreasing the rate at which we use these fuels does not stop the problem, but only delays the result.

### Alternative Energy Sources

• Switching Energy Sources is an alternative to using all of the fossil fuels up.

• Unfortunately this is very expensive, and is difficult to implement into society.

• Until we find an alternative source, our best bet is to conserve what we have now.

### Cogeneration

• The process in which industries use the waste material from one process to power a second process.

• Ex. Using the steam from thermal power stations to heat nearby buildings before being heated again in the thermal power station.

### How could you conserve energy?

• Turn off unused appliances

• Turn down thermostat (where more clothes)

• Car pool, or take public transport

• Avoid energy wasting appliances and gadgets.

• Reduce water consumption (in shower, sink, watering lawns, etc..)

### Sustainable Developement

• Economic Development that meets current needs without compromising the ability of future generations to meet their needs.