Math
Visual
Sankey
100
The energy efficiency of a process is equal to the useful energy output divided by the...
total energy input.
100
A Sankey diagram shows...
a.which forms of energy are kinetic energy and which forms are potential energy.
b.changes in the forms and relative amounts of energy in an event or process.
c. the interactions of energy and mass in an event or process.
d.a closed system.
b
100
Marcus and Brianna are drawing a Sankey diagram. Marcus says that the thermal energy produced by an appliance is always non-useful energy. Brianna disagrees. Who is correct, and why?
Brianna is correct because thermal energy can be a useful energy output.
200
A 90% efficient electric heater produces 900 joules of useful energy per second. What is the energy input?
1,000J
200
Which equation is used to calculate efficiency?
200
Sassiane and Sean are drawing a Sankey diagram of a car. Most of the energy output is thermal energy. Sassiane says they should make the thermal energy arrow straight because it represents the greatest percentage of energy output. Sean says they should make the thermal energy arrow curve down because it represents useful energy. Which student is correct?
Neither is correct.
300
A bicycle is 70% efficient. What is the total energy input of the bicycle if the useful energy output is 420 joules per second?
600 J/s.
300
Mary uses this equation to calculate energy efficiency as a percentage. What mistake does she make in the equation?
She reverses the quantities in the ratio.
300
In this Sankey diagram, the rectangle labeled 1 represents energy that is...
input into the machine.
400
A small fan uses 45 joules of electric energy per second. It uses 30 joules to move air, 10 joules to heat the room, and 5 joules to make sound. The useful energy is the energy used to move air.
What is the energy efficiency of the fan?
67%
400
This Sankey diagram represents the flow of electric energy into a television. The television transforms 75% of the energy input into light and 5% of the energy input into sound. The remaining 20% of the energy input is transformed into thermal energy.
Which part of the Sankey diagram represents sound energy?
3
400
In a Sankey diagram, what does the thickness of the lines represent?
The relative amounts of energy.
500
A 90% efficient television uses 300 joules of electric energy per second. The amount of light the television produces is eight times the amount of sound. How much light and how much sound does the television produce each second?
240 J light and 30 J sound.
500
This Sankey diagram shows the energy changes in a car. Each form of energy output is 25% of the total output.
Which statement about this diagram is true?
About 25% of the energy output is useful.
500
This Sankey diagram shows the energy transformations in a blender per second of use. What is the efficiency of the blender?
80%