Energy efficiency

The law of conservation of energy states that when one form of energy is converted into another,

• energy is destroyed in the process
• no energy is destroyed in the process
• energy is created in the process
• some amount of energy cannot be accounted for

In energy transformations, "wasted energy" usually takes what form?

• heat
• chemical energy
• light
• sound waves

Efficiency is calculated by useful energy output divided by total energy input, expressed as a percentage

• False

• True

An oven uses 400 J of electricity to produce 300 J of heat. How efficient is it?

• 133 %

• 75 %

• 300 %

• .75 %

A blender uses 1000 J of energy to spin it's blades and make smoothies. What is the input energy?

• Electrical

• Sound

• Heat

• Mechanical

A car uses 100 J of gasoline. 83 J are turned into mechanical energy. How much should be turned into heat?

• 7 J

• 17 J

• 83 J

• 100 J

What is the equation for energy efficiency?

An oven uses energy to produce heat, light, and sound. If it produces 400 J of heat, 75 J of light, and 50 J of sound, how much input energy did it have?

• 400 J

• 500 J

• 525 J

• 375 J

Total energy in has to equal

• Total energy out (wasteful + useful)

• Useful energy out

• Useful out - wasteful

A TV uses 200 J of electricity and transforms it into 125 J of sound and light and 75 J of heat. How efficient is it?

• 62.5%

• .625%

• 37.5%

• .375%