Efficiency Efficiency Ratio of useful energy output to

Efficiency

Efficiency • Ratio of useful energy output to the energy input • Ex: Incandescent Light Bulb ▫ 5% of energy used is useful (Light) ▫ 95% of energy is wasted as heat ▫ 5% efficient

Efficiencies • Candle – 0. 04% • 100 W Incandescent – 2. 6% • Projection bulb incandescent – 5. 1% • Fluorescent Bulb – 11 -15% • Light Emitting Diode (LED) – 12%

Phasing Out Incandescent Bulbs • Europe, Canada, US and many other countries have started to phase out incandescent light bulbs due to their inefficiency

Where: Eout – Useful energy output Ein – Energy input

Where: Pout – Useful power output Pin – Power input

Example 1: • Your car’s engine takes in 10, 000 J of energy per second. The energy output measured in the car’s motion forward is 1, 600 J per second of kinetic energy. What is the efficiency of the car?

• Power – Pg 175 # 1, 2, 4, 5 • Efficiency - Pg 182 # 1 -4

Overall Efficiency • Used to calculate the accumulated efficiency of a process

Become a Vegetarian • Each step up the food chain is about 10% efficient • So if cows need to eat 100, 000 J of plant energy to grow and live, humans only get 10, 000 J of that energy • So one vegetarian is equivalent to 10 meat eaters

Ex 2: 100 J of energy is produced by Niagara Falls. Long distance power lines are 99. 5% efficient, local power lines are 99% efficient, if you use: a) Incandescent bulbs (5. 1% efficient), how much useful energy do you receive? b) Fluorescent bulbs (12% efficient), how much energy do you receive?

• Pg 194 # 1 • Pg 195 # 2 -4 • Read 197 and make notes on ways to generate electricity more efficiently