Energy Efficiency

The Law of Conservation of Energy states:

• Energy can created or destroyed but not transformed

• Energy cannot be created or destroyed, it can only transformed

• Energy can't be created, destroyed or transformed

• Energy cannot be created or destroyed.

What kind of energy does an object possess when it's resting on top of the hill?

• Potential Energy

• Chemical Energy

• Kinetic Energy

• All of the above

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%

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

• 5%

• 50%

• 55%

• 100%

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

No machine in existence has 100% efficiency due to ____________________.

• magic
• friction
• smoke
• input

A car transfers 100 J of chemical energy in order to gain 50 J of kinetic energy. The efficiency of the car is

• 20%

• 0.5%

• 50%

• 200%

Total energy = 200J
Useful energy = 20J

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

• 100%

• 80%

• 40%

• 10%

Total energy = 350J
Useful energy = 70J

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

• 100%

• 80%

• 40%

• 20%

This car needs 8600J of energy to power it. If 5000J is changed into useful energy, how much energy is wasted?

• 13600J

• 3600J

• 5000J

• 8600J