Energy Efficiency and Sankey Diagrams

The video tutorial explains the purpose of light bulbs and how they convert electrical energy into light and thermal energy. It introduces the concept of energy systems, highlighting input, useful, and wasted energy. The tutorial uses a Sankey diagram to visually represent these energy transfers. An example is provided with a light bulb, showing how energy is distributed between light and heat. The video also covers how to scale Sankey diagrams and calculate the efficiency of a light bulb using a specific formula.

What is the primary purpose of using a light bulb?

• To see in the dark by converting electrical energy into light energy

• To store electrical energy

• To convert light energy into electrical energy

• To generate heat

In an energy system, what are the three types of energy involved?

• Input energy, kinetic energy, and potential energy

• Input energy, useful output energy, and wasted output energy

• Thermal energy, light energy, and sound energy

• Chemical energy, nuclear energy, and mechanical energy

What does a Sankey diagram represent in an energy system?

• The storage of energy in a system

• The increase of energy efficiency

• The conversion of thermal energy to light energy

• The flow of energy from input to useful and wasted outputs

In the given Sankey diagram example, if the input energy is 50 joules, how much energy is wasted?

• 10 joules

• 20 joules

• 30 joules

• 50 joules

How is the scale of a Sankey diagram determined in the given example?

• By the width of the arrows

• By the length of the arrows representing energy values

• By the height of the arrows

• By the color of the arrows

What is the formula to calculate the efficiency of a light bulb?

• Efficiency = Total input energy / Wasted output energy

• Efficiency = Total input energy / Useful output energy

• Efficiency = Wasted output energy / Total input energy

• Efficiency = Useful output energy / Total input energy

What is the efficiency percentage of the light bulb in the example?

• 50%

• 30%

• 60%

• 40%