lesson 11 — 2.10
Energy
Calculations + §2.6 & 2.7
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Slide 1: Slide
energy calculationsMiddelbare schoolhavo, vwoLeerjaar 1
This lesson contains 20 slides, with text slides and 1 video.
Items in this lesson
Energy
Calculations + §2.6 & 2.7
Slide 1 - Slide
Slide 2 - Video
In pairs of two
Step 1)
For 10 minutes
- One of you reads and takes notes of §2.6.
- The other reads and takes notes of §2.7
Step 2)
Discuss what you learned
- Go over each others notes
- think of one question per paragraph
Step 3
- Share your notes with another pair close to you
Slide 3 - Slide
Recap
Slide 4 - Slide
- Useful energy
- wasted energy
- Efficiency
Slide 5 - Slide
Efficiency=(totalenergyusefulenergy)⋅100
%
Slide 6 - Slide
Efficiency=(totalenergyusefulenergy)⋅100
%
=(EtEu)⋅100
%
η
- η: efficiency (%)
- Eu: Energy useful (J)
- Et: energy total (J)
Slide 7 - Slide
2.10
Slide 8 - Slide
Which lamp is more efficient?
A
B
Slide 9 - Slide
Slide 10 - Slide
Calculations — Exercise 1
Consider a machine that puts out 6070 joules of useful work. As a by product it also produces 2500Joules of heat.
Calculate the efficiency of this machine.
Slide 11 - Slide
Consider a machine that puts out 6070 joules of useful work. As a by product it also produces 2500Joules of heat.
Calculate the efficiency of this machine.
Given
- Eu = 6070 J
- Ew = 2500 J
- Et = 6700 + 2500 = 8570 J
Asked
- Calculate the efficiency of this machine
Fromula
Calculation
Slide 12 - Slide
Consider a machine that puts out 6070 joules of useful work. As a by product it also produces 2500Joules of heat.
Calculate the efficiency of this machine.
Given
- Eu = 6070 J
- Ew = 2500 J
- Et = 6700 + 2500 = 8570 J
Asked
- Calculate the efficiency of this machine
Fromula
Calculation
=(EtEu)⋅100
η
%
Slide 13 - Slide
Consider a machine that puts out 6070 joules of useful work. As a by product it also produces 2500Joules of heat.
Calculate the efficiency of this machine.
Given
- Eu = 6070 J
- Ew = 2500 J
- Et = 6700 + 2500 = 8570 J
Asked
- Calculate the efficiency of this machine
Fromula
Calculation
=(EtEu)⋅100
η
%
=(85706070)⋅100
η
% = 70,8 %
Slide 14 - Slide
Calculations — Exercise 2
A machine has an efficiency of 25 %. It creates 350 joules of useful work. Calculate its total energy input.
Slide 15 - Slide
A machine has an efficiency of 25 %. It creates 350 joules of useful work. Calculate its total energy input.
Given
- η = 25 %
- Euseful = 350 J
Asked
- Calculate the total energy input of this machine
Fromula
Calculation
Slide 16 - Slide
Given
- η = 25 %
- Euseful = 350 J
Asked
- Calculate the total energy input of this machine
Fromula
Calculation
Slide 17 - Slide
Calculations — Exercise 3
An average car uses 8.9 liters of gasoline per 100 kilometre. One liter of gasoline contains 31536000 joules. If a car drives 150 kilometre, and during this journey it creates 32450544 joules of heat and sound energy combined, what would be its efficiency?
Slide 18 - Slide
An average car uses 8.9 liters of gasoline per 100 kilometre. One liter of gasoline contains 31536000 joules. If a car drives 150 kilometre, and during this journey it creates 32450544 joules off heat and sound energy combined, what would be its efficiency?
Given
- 8.9 liters per 100 kilometer
- one liter contains 3153600 joules
- a car drives 150 kilometrer
- EWasted = 32450544 J
- Etotal = 8.9 x 3153600 x 1.5 = 42100560 J
- Euseful = 42100560 - 32450544 =
9650016 J
Slide 19 - Slide
Given
- 8.9 liters per 100 kilometer
- one liter contains 3153600 joules
- a car drives 150 kilometrer
- EWasted = 32450544 J
- Etotal = 8.9 x 3153600 x 1.5 = 42100560 J
- Euseful = 42100560 - 32450544 =
9650016 J
