2-7 efficiency (4.4)

• Natuurkunde
• Middelbare school
• havo
• Leerjaar 3

Efficiency (4.4) 

Stationary

- Writingbook, iPad

- Pen, pencil, geotriangle

- Calculator

Schoolbags in

the cupboard

Phones in the phone bag

Bluetooth 

- ON

- VPN off

Lesson goals:

• Explain what efficiency is.
• Explain how you can make your energy usage sustainable.
• Calculate efficiency with the following equations:

• Calculate the efficiency of a boiler.

E​nut​​=Q=c⋅m⋅ΔT

Sustainable energy usage

Efficiency indicates whichpotion of the available energy is usefully consumed.

Calculating efficiency

blz 158

3,8 J of 6,5 J energy is converted into light in a lightbulb. What is the efficiency of the lightbulb?

1. 171%
2. 58%
3. 37%
4. 15%

Efficiency of a boiler

E_tot = Calculate the ammount of heat: 

                     volume x calorific value

The calorific value of methane gas (natural gas) is 32 MJ/m³

^E_usefull = Q =

c⋅m⋅ΔT

E_useful in a boiler

c = specific heat of water

m = mass (of water)

      = change in T in ⁰C

E​usefull​​=Q=c⋅m⋅ΔT

ΔT

What is the energy used if 16 liter of water increases temperature from 13 to 98 degrees Celsius. Show all your calculations.

Bereken de hoeveelheid warmte van 0,35 m3 aardgas. Vul alleen je antwoord zonder eenheid in. gebruik een , en niet een .

Calculate the heat released by 0,35 m3 natural gas. Show your calculations.

                        Now make the test yourself paragraph 4.4

     and then question 40, 41 and 44