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

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-2

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

• heat
• chemical energy
• light
• sound waves

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NGSS.MS-PS3-3

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

• False

• True

Energy efficiency of incandescent lightbulbs is

• 50%

• 25%

• 15%

• 5%

Tags

NGSS.MS-PS3-3

Total energy = 350J
Useful energy = 70J

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

• 100%

• 80%

• 40%

• 20%

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%

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

Which of the following energy transformations occur when a lamp that is plugged into a wall socket is functioning correctly?

• Chemical to light
• Electrical to chemical
• Electrical to light
• Chemical to electrical

What accounts for the most energy use in American homes?

• Heating and cooling

• Water heating

• Electronics and lighting

• Appliances

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

Tags

NGSS.MS-PS3-4

What is the unit for Power?

• Joules

• Volts

• Watts

• Amps

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5