Energy Efficiency Calculations

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

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

What does this equation mean? \(\frac{useful\ output}{input}\ \times\ 100\%\) 

• Efficiency is the fraction of output energy that is useful, compare to how much energy you put in.

• Nothing, it's just math. 

• Efficiency compares what useful energy you get out to how much you have to put in.

• Efficiency compares how much you put in to how much you get out, whether it is the type you want or not.

Tags

NGSS.MS-PS3-5

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%

My dog likes to run and bark. If he eats 1000 J of food, and transforms that into 700 J of kinetic energy, 100 J of sound, and 200 J of heat, what is his efficiency?

• 80%

• 70%

• 20%

Tags

NGSS.MS-PS3-5

What is the efficiency of the machine if the input is 263 J and the output is 142 J?

• 6.26%

• 54%

• 100%

• 260%

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

• 100%

• 80%

• 40%

• 10%

Tags

NGSS.MS-PS3-3

• 100%

• 80%

• 40%

• 20%

• 100%

• 10%

• 40%

• 20%

Tags

NGSS.MS-PS3-5

What is the formula for calculating energy efficiency?

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

A light bulb uses 60 J of electrical energy and emits 15 J of light energy. What is its efficiency?

• 25%

• 50%

• 75%

• 100%

Tags

NGSS.MS-PS3-4