Work, Power and Efficiency knowledge check

We can calculate power by

• multiplying work and time

• dividing work by time

• multiplying force and work

• dividing force by work

You do 90 joules of work in 30 seconds. How much power have you generated?

• 30 watts
• 3 watts
• 120 watts
• 270 watts

Work divided by time equals...

• energy
• power

The unit of work is the ...

• joule
• force

Tags

NGSS.HS-PS3-2

The unit of power is the...

• work
• watt

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

Tags

NGSS.HS-PS3-3

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

• heat
• chemical energy
• light
• sound waves

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-3

Total energy = 200J
Useful energy = 20J

Workout the efficiency of this lightbulb.
 $efficiency\ =\ \frac{useful\ enegy}{total\ energy\ in}\ \times100$  

• 100%

• 80%

• 40%

• 10%

Tags

NGSS.HS-ETS1-3

NGSS.HS-PS3-4

Total energy = 350J
Useful energy = 70J

Workout the efficiency of this iphoneX.
 $efficiency\ =\ \frac{useful\ energy}{total\ energy\ in}\ \times100\%$  

• 100%

• 80%

• 40%

• 20%

Which of these equations is correct?

•  $efficiency\ =\ \frac{useful\ energy\ transferred}{total\ energy\ transferred}$  

•  $efficiency\ =\ \frac{total\ energy\ transferred}{useful\ energy\ transferred}$  

•  $energy\ =\ efficiency\ \times100\%$  

•  $efficiency\ =\ \frac{wasted\ energy\ transferred}{total\ energy\ tranferred}$