Energy Efficiency Calculations

What percent energy is wasted by a machine if the energy input is 262 J and the energy output is 131 J?

• 5%

• 50%

• 100 J

A washing machine uses 250J of electrical energy to produce 125J of useful energy. How efficient is it?

• 5%

• 50%

• 55%

• 100%

Calculate the efficiency of a light bulb if the energy input is 125J but the useful energy output is 25J

• 20%

• 100%

• 50%

• 75%

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

• False

• True

What is the energy efficiency of hydroelectric dams?

• 90%

• 70%

• 50%

• 29%

Tags

NGSS.MS-PS3-3

How much light energy in converted to electrical energy in commercial solar panels?

• 75%

• 60%

• 20%

• 5%

Tags

NGSS.HS-PS3-3

A kettle uses 100J of electrical energy to produce 7J of sound energy and 93J of thermal energy. How efficient is the kettle?

• 100%

• 7%

• 93%

• 95%

What type of device might this Sankey be about?

• A very efficient LED light bulb

• A very inefficient incandescent light bulb

• A coal power plant

• A wind turbine

Tags

NGSS.MS-PS3-3

NGSS.MS-PS3-4

A refrigerator uses 500J of electrical energy to remove 150J of heat from its interior. What is its energy efficiency?

• 30%

• 50%

• 70%

• 90%

Tags

NGSS.MS-PS3-3

If a car engine converts 2000J of chemical energy from fuel into 400J of mechanical energy, what is the efficiency of the engine?

• 10%

• 20%

• 30%

• 40%