Efficiency (2 lessons)

• Natuurkunde
• Middelbare school
• vwo
• Leerjaar 3

If you have a watercooker which has 1200 W of power, and uses 7,5 minutes to boil 800 mL of water (from 20 degrees) determine what its efficiency is.

You have a boiler in your house which has an efficiency of 92%, with this boiler you use 1500 m³ of gas per year to heat your house. Sadly the boiler breaks down and you have to install a temporary old boiler until you can get a proper replacement, your temporary boiler has an efficiency of 76%. How much more gas do you need to use if it takes exactly one year to change back to a better boiler?

You have a boiler in your house which has an efficiency of 92%, with this boiler you use 1500 m3 of gas per year to heat your house.
How much energy is used efficiently?

your temporary boiler has an efficiency of 76%. The amount of efficiently used energy is still the same, but the total used amount of gas will change, what will it be now?

You have a boiler in your house which has an efficiency of 92%, with this boiler you use 1500 m3 of gas per year to heat your house. After it dies your temporary boiler has an efficiency of 76%. How much more gas do you need to use if it takes exactly one year to change back to a better boiler?

a 1200W Watercooker with 83% efficiency gets 18 degrees water to boil, there is 2,3 L of water.​

1: How much heat is required to get all the water to boil?​

Q = c x m x ΔT Q = 4,2 x 2300 x 82 = 792120 J of heat

2: How much electric energy is required?​

792120 J of heat is 83% of what the watercooker is given in electrical energy so
792120 / 83% x 100% = 954361 Joules of electrical energy
​3: How long does it take the 1200W watercooker to boil all the water?​

How much electrical energy will it take an electrical boiler installation (with a efficiency of 76%) to heating 2 million L of water from 16 to 19 degrees at the outdoors swimmingpool in Zwolle?